Heavy Duty Shipping Boxes (Double Wall, ECT-44 to ECT-51)

IN STOCK Industrial-grade 12
Boxes - Corrugated

12x12x8 ECT-48 Double Wall Corrugated Boxes - Heavy Duty, Bundle of 15

PN: HD12128DW

12 x 12 x 8 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$34.80 / BUNDLE
IN STOCK Industrial-grade 12x12x8 heavy-duty corrugated boxes engineered for demanding warehouse operations. Built with ECT-44 single-wall kraft construction–40% stronger than standard shipping containers–for superior stacking performance and product protection. Sold flat in convenient bundles of 25 to maximize storage and freight efficiency.
Boxes - Corrugated

12x12x8 Heavy-Duty ECT-44 Kraft Corrugated Boxes - 25/Bundle

PN: HD12128

12 x 12 x 8 in ECT-44 Single Wall Corrugated 25 PER BUNDLE
$70.63 / BUNDLE
IN STOCK ECT-48 double wall kraft corrugated boxes deliver maximum protection for mid-size shipments. 12
Boxes - Corrugated

12x12x6 ECT-48 Double Wall Kraft Boxes - Heavy Duty Shipping, Bundle of 15

PN: HD12126DW

12 x 12 x 6 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$31.02 / BUNDLE
IN STOCK Heavy-duty ECT-44 kraft corrugated boxes built 40% stronger than standard single wall cartons for superior stacking performance and freight protection. 12
Boxes - Corrugated

12x12x6 Heavy-Duty ECT-44 Kraft Corrugated Boxes - 25 Bundle

PN: HD12126

12 x 12 x 6 in ECT-44 Single Wall Corrugated 25 PER BUNDLE
$39.89 / BUNDLE
IN STOCK ECT-71 heavy-duty double wall corrugated boxes engineered for maximum protection and stacking performance. These 12x12x12 kraft cartons deliver 140# capacity per parcel standards, reducing freight costs through optimal cube utilization. Bundle of 15 boxes.
Boxes - Corrugated

12x12x12 ECT-71 Heavy-Duty Double Wall Boxes - 140# Capacity, Bundle of 15

PN: HD121212HDDW

12 x 12 x 12 in ECT-71 Double Wall Corrugated 15 PER BUNDLE
$131.31 / BUNDLE
IN STOCK Heavy-duty ECT-48 double wall corrugated construction delivers superior stacking strength and crush resistance for demanding warehouse and fulfillment operations. These kraft 12x12x12 shipping cartons are manufactured to handle high-volume distribution while protecting contents. Bundle of 15 boxes ships flat to maximize storage efficiency and reduce freight costs.
Boxes - Corrugated

12x12x12 ECT-48 Double Wall Corrugated Boxes - Heavy Duty, Bundle of 15

PN: HD1212DW

12 x 12 x 12 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$35.77 / BUNDLE
IN STOCK Engineered for hazardous materials compliance: these ECT-44 single wall corrugated boxes ship 4 one-gallon plastic jugs safely per UN 4G/Y19.7 and 4G/Y19.8 standards. Kraft construction with pre-printed warning labels and directional arrows. Flat-ship design cuts storage footprint by 40% versus assembled inventory.
Boxes - Corrugated

12.25x12.25x12.75 ECT-44 Haz Mat Corrugated Box - 4 Gallon Jug Capacity, Bundle of 20

PN: HAZ1052

12 1/4 x 12 1/4 x 12 3/4 in ECT-44 Single Wall Corrugated 20 PER BUNDLE
$198.70 / BUNDLE
IN STOCK Professional-grade 16x10x6 double wall corrugated boxes engineered for demanding warehouse and fulfillment operations. ECT-48 kraft construction delivers superior stacking performance and impact protection–ideal for protecting mid-weight products during transport and storage. Ships flat in bundles of 15 to maximize warehouse efficiency and reduce freight costs.
Boxes - Corrugated

16x10x6 Double Wall Corrugated Boxes ECT-48 Kraft - Bundle of 15

PN: HD16106DW

16 x 10 x 6 in D.W./ECT-48 Corrugated 15 PER BUNDLE
$50.59 / BUNDLE
IN STOCK Heavy-duty ECT-48 double wall corrugated boxes designed for demanding warehouse operations. 14
Boxes - Corrugated

14x12x10 ECT-48 Double Wall Shipping Boxes - Heavy-Duty Kraft, Bundle of 15

PN: HD141210DW

14 x 12 x 10 in D.W./ECT-48 Corrugated 15 PER BUNDLE
$67.77 / BUNDLE
IN STOCK Industrial-grade ECT-44 single wall kraft corrugated boxes designed for warehouse managers who need maximum stacking performance and protection. These 14x12x10 heavy-duty cartons deliver 40% greater strength than standard shipping containers, reducing damage rates and freight loss. Ships flat in convenient bundles of 25 for efficient storage and deployment.
Boxes - Corrugated

14x12x10 ECT-44 Heavy-Duty Kraft Corrugated Boxes - 40% Stronger, Bundle of 25

PN: HD141210

14 x 12 x 10 in ECT-44 Single Wall Corrugated 25 PER BUNDLE
$53.40 / BUNDLE
IN STOCK These 13x13x13
Boxes - Corrugated

13x13x13" ECT-44 Heavy-Duty Kraft Corrugated Boxes - Bundle of 25

PN: HD131313

13 x 13 x 13 in ECT-44 Single Wall Corrugated 25 PER BUNDLE
$106.52 / BUNDLE
IN STOCK ECT-48 heavy-duty double wall corrugated boxes sized 16
Boxes - Corrugated

16x10x10 Double Wall Kraft Corrugated Boxes ECT-48 - Bundle of 15

PN: HD161010DW

16 x 10 x 10 in D.W./ECT-48 Corrugated 15 PER BUNDLE
$56.86 / BUNDLE
IN STOCK Ship hazardous materials safely with these UN 4G/Y37.6/S certified haz mat boxes designed for 1–5 gallon containers. Built from ECT-51 double wall kraft corrugated, they deliver superior stacking strength and crush resistance. Bundle of 10 ships flat to maximize warehouse space and reduce freight costs.
Boxes - Corrugated

12 1/8x12 1/8x13 9/16 ECT-51 Haz Mat Boxes - UN Certified, Bundle of 10

PN: HAZCO15G

12 1/8 x 12 1/8 x 13 9/16 in ECT-51 Double Wall Corrugated 10 PER BUNDLE
$92.72 / BUNDLE
IN STOCK Heavy-duty ECT-44 kraft corrugated shipping boxes deliver 40% greater strength than standard containers, maximizing stacking performance and freight efficiency. 15
Boxes - Corrugated

15x12x10 ECT-44 Heavy-Duty Kraft Corrugated Boxes - Bundle of 25

PN: HD151210

15 x 12 x 10 in ECT-44 Single Wall Corrugated 25 PER BUNDLE
$88.99 / BUNDLE
IN STOCK Heavy-duty ECT-48 double wall corrugated boxes deliver maximum protection for mid-weight shipments and storage. Each 13x13x13 kraft carton offers superior stacking strength and crush resistance. Bundle of 15 ships flat to maximize your warehouse efficiency and minimize storage footprint.
Boxes - Corrugated

13x13x13 ECT-48 Double Wall Corrugated Boxes - Heavy Duty, Bundle of 15

PN: HD1313DW

13 x 13 x 13 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$47.07 / BUNDLE
IN STOCK Industrial-grade ECT-48 double wall corrugated boxes engineered for maximum stacking performance and freight efficiency. 15x12x12
Boxes - Corrugated

15x12x12 ECT-48 Double Wall Kraft Boxes - Heavy Duty Shipping, 15-Pack

PN: HD151212DW

15 x 12 x 12 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$67.58 / BUNDLE
IN STOCK Heavy-duty ECT-48 kraft double wall corrugated boxes engineered for maximum protection and stacking performance. 15x12x10 dimensions ideal for mid-weight industrial shipments. Sold as a bundle of 15 cartons that ship flat to reduce warehouse footprint and freight costs.
Boxes - Corrugated

15x12x10 Double Wall Corrugated Boxes ECT-48 Kraft - Bundle of 15

PN: HD151210DW

15 x 12 x 10 in D.W./ECT-48 Corrugated 15 PER BUNDLE
$70.25 / BUNDLE
IN STOCK 11.5x11.5x15.4 ECT-48 Double Wall Kraft Boxes - Shipping Cartons, Bundle of 25
Boxes - Corrugated

11 1/2" x 11 1/2" x 15.4" ECT-48 Kraft Shipping Boxes, 25-Pack

PN: KEG1

11 1/2 x 11 1/2 x 15 3/8 in ECT-48 Double Wall Corrugated 25 PER BUNDLE
$65.70 / BUNDLE
IN STOCK DOT-compliant hazmat shipping boxes designed for 1-gallon F-style paint cans. Each carton holds 4 cans with ECT-44 single-wall corrugated kraft construction. Pre-printed with mandatory warnings and directional arrows. Ships flat to maximize warehouse storage efficiency.
Boxes - Corrugated

16x11x12 ECT-44 Hazmat Shipping Boxes, 10-Pack

PN: HAZ1049

16 x 11 x 12 in ECT-44 Single Wall Corrugated 10 PER BUNDLE
$147.20 / BUNDLE
IN STOCK ECT-44 single wall kraft corrugated boxes deliver 40% greater strength than standard shipping cartons, making them ideal for high-stack warehouse environments. At 16
Boxes - Corrugated

16x12x10 ECT-44 Heavy-Duty Kraft Corrugated Boxes - 40% Stronger, Bundle of 25

PN: HD161210

16 x 12 x 10 in ECT-44 Single Wall Corrugated 25 PER BUNDLE
$105.96 / BUNDLE
IN STOCK Heavy-duty ECT-44 single wall kraft corrugated boxes built 40% stronger than standard shipping containers. 16
Boxes - Corrugated

16x12x8 ECT-44 Heavy-Duty Kraft Corrugated Boxes - Bundle of 25

PN: HD16128

16 x 12 x 8 in ECT-44 Single Wall Corrugated 25 PER BUNDLE
$52.44 / BUNDLE
IN STOCK Premium ECT-48 double wall corrugated boxes designed for demanding shipping and storage applications. These 14x14x10 kraft cartons deliver superior stacking strength and puncture resistance to protect high-value freight. Sold in bundles of 15 and ship flat to minimize warehouse footprint and reduce freight costs.
Boxes - Corrugated

14x14x10 ECT-48 Double Wall Corrugated Boxes - Heavy-Duty Protection, Bundle of 15

PN: HD141410DW

14 x 14 x 10 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$45.15 / BUNDLE
IN STOCK Industrial-grade ECT-44 single wall kraft corrugated boxes engineered for maximum stacking strength and cost efficiency. These 14x14x10 shipping cartons are 40% stronger than standard containers, ideal for high-volume fulfillment centers. Bundle of 25 sold and shipped flat.
Boxes - Corrugated

14x14x10 ECT-44 Heavy-Duty Kraft Corrugated Boxes - 25 Pack Bundle

PN: HD141410

14 x 14 x 10 in ECT-44 Single Wall Corrugated 25 PER BUNDLE
$110.28 / BUNDLE
IN STOCK Premium ECT-48 double wall corrugated boxes designed for high-performance shipping and storage. These 16
Boxes - Corrugated

16x12x12 ECT-48 Double Wall Corrugated Boxes - Bundle of 15

PN: HD161212DW

16 x 12 x 12 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$46.21 / BUNDLE
IN STOCK Heavy-duty ECT-44 kraft corrugated boxes engineered for demanding warehouse and fulfillment operations. These 16x12x12 single wall shipping cartons deliver 40% greater stacking strength than standard containers, reducing damage claims and optimizing pallet density. Sold flat in convenient bundles of 15 for maximum volume efficiency.
Boxes - Corrugated

16x12x12 ECT-44 Heavy-Duty Kraft Corrugated Boxes - Bundle of 15

PN: HD161212

16 x 12 x 12 in ECT-44 Single Wall Corrugated 15 PER BUNDLE
$36.96 / BUNDLE
IN STOCK ECT-48 double wall corrugated boxes engineered for maximum protection and stacking performance. These 16x12x10 kraft cartons deliver heavy-duty construction at scale–ship flat in bundles of 15 to cut storage overhead and freight costs. Ideal for high-volume fulfillment operations.
Boxes - Corrugated

16x12x10 ECT-48 Double Wall Corrugated Boxes - Heavy-Duty Kraft, Bundle of 15

PN: HD161210DW

16 x 12 x 10 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$64.62 / BUNDLE
IN STOCK Ship with confidence using these 16x12x8 double wall corrugated boxes engineered with ECT-48 kraft material for maximum stacking performance and freight protection. Each bundle of 15 ships flat, reducing storage footprint and freight costs by up to 40% compared to assembled alternatives. Ideal for warehouse managers moving mid-weight products with zero damage tolerance.
Boxes - Corrugated

16x12x8 Double Wall Corrugated Boxes ECT-48 Kraft - Bundle of 15

PN: HD16128DW

16 x 12 x 8 in D.W./ECT-48 Corrugated 15 PER BUNDLE
$58.64 / BUNDLE
IN STOCK Engineered for maximum protection and stacking performance, these 16
Boxes - Corrugated

16x12x6 Double Wall Corrugated Boxes ECT-48 Kraft - Bundle of 15

PN: HD16126DW

16 x 12 x 6 in D.W./ECT-48 Corrugated 15 PER BUNDLE
$58.49 / BUNDLE
IN STOCK ECT-44 single wall kraft corrugated boxes deliver 40% greater stacking strength than standard shipping containers–ideal for high-volume fulfillment centers and warehouse operations. Each 14x14x14
Boxes - Corrugated

14x14x14" ECT-44 Heavy-Duty Corrugated Boxes - 25-Pack Bundle

PN: HD141414

14 x 14 x 14 in ECT-44 Single Wall Corrugated 25 PER BUNDLE
$68.63 / BUNDLE
IN STOCK ECT-48 rated double wall kraft boxes deliver industry-standard protection for medium-weight shipments. Each 14
Boxes - Corrugated

14x14x12 ECT-48 Double Wall Kraft Boxes - Heavy Duty Shipping, 15-Pack

PN: HD141412DW

14 x 14 x 12 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$91.63 / BUNDLE
IN STOCK ECT-48 double wall corrugated kraft boxes engineered for maximum durability and stacking performance. 14
Boxes - Corrugated

14x14x8 ECT-48 Double Wall Kraft Boxes - Heavy Duty Shipping Cartons, Bundle of 15

PN: HD14148DW

14 x 14 x 8 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$64.70 / BUNDLE
IN STOCK Packrift's 14x14x6 double wall corrugated boxes deliver ECT-48 rated strength for demanding logistics operations. Heavy-duty kraft construction ensures products arrive damage-free while maximizing stacking performance. Bundle of 15 units ships flat, reducing storage footprint and freight costs.
Boxes - Corrugated

14x14x6 ECT-48 Double Wall Corrugated Boxes - Heavy-Duty Shipping, Bundle of 15

PN: HD14146DW

14 x 14 x 6 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$58.64 / BUNDLE
IN STOCK ECT-48 double-wall corrugated hazmat shipping boxes engineered for 5-gallon pail transport. Each bundle includes 10 boxes (12.5
Boxes - Corrugated

12 1/2" x 12 1/2" x 15 1/10" ECT-48 Hazmat Shipping Boxes, 10-Pack

PN: HAZCO15GP

12 1/2 x 12 1/2 x 15 1/8 in ECT-48 Double Wall Corrugated 10 PER BUNDLE
$95.73 / BUNDLE
IN STOCK Enterprise-grade ECT-48 double wall corrugated boxes built for high-velocity fulfillment centers and warehouse operations. These 12.5
Boxes - Corrugated

12.5x12.5x15 ECT-48 Double Wall Corrugated Boxes - Heavy Duty Shipping Cartons, Bundle of 15

PN: HD121215DW

12 1/2 x 12 1/2 x 15 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$47.18 / BUNDLE
IN STOCK ECT-48 double wall corrugated boxes designed for maximum protection and stacking performance. These 14x14x14 kraft cartons deliver heavy-duty strength for demanding shipments, warehouses, and fulfillment operations. Sold in bundles of 15 and ship flat to maximize storage efficiency.
Boxes - Corrugated

14x14x14 ECT-48 Double Wall Boxes - Heavy Duty Kraft Cartons, Bundle of 15

PN: HD141414DW

14 x 14 x 14 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$48.46 / BUNDLE
IN STOCK Heavy-duty double wall corrugated boxes built for high-performance warehousing. These 14x14x14 ECT-71 kraft cartons deliver maximum stacking strength while shipping and storing flat to reduce storage overhead. Bundle of 15 boxes per unit.
Boxes - Corrugated

14x14x14 ECT-71 Heavy-Duty Double Wall Boxes - 15-Pack Bundle

PN: HD141414HDDW

14 x 14 x 14 in ECT-71 Double Wall Corrugated 15 PER BUNDLE
$131.22 / BUNDLE
IN STOCK ECT-48 double wall kraft corrugated cartons engineered for maximum protection and stacking performance in warehouse and fulfillment operations. 12x12x16
Boxes - Corrugated

12x12x16 ECT-48 Double Wall Shipping Boxes - Heavy-Duty Protection, Bundle of 15

PN: HD121216DW

12 x 12 x 16 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$62.71 / BUNDLE
IN STOCK Kraft ECT-51 double wall corrugated haz mat boxes engineered for safe transport of 4 x 1-gallon containers. Pre-printed with mandatory UN 4G warning labels and directional arrows. Ships and stores flat–10 cartons per bundle.
Boxes - Corrugated

14.25x14.25x7.625 ECT-51 Haz Mat Boxes - 4-Gallon Capacity, Bundle of 10

PN: HAZCO4G

14 1/4 x 14 1/4 x 7 5/8 in ECT-51 Double Wall Corrugated 10 PER BUNDLE
$131.42 / BUNDLE
IN STOCK Upgrade to ECT-44 heavy-duty corrugated boxes that deliver 40% greater stacking strength than standard shipping containers. These 16
Boxes - Corrugated

16x14x10 ECT-44 Heavy-Duty Corrugated Boxes, Bundle of 25

PN: HD161410

16 x 14 x 10 in ECT-44 Single Wall Corrugated 25 PER BUNDLE
$123.43 / BUNDLE
IN STOCK ECT-48 rated heavy-duty double wall cartons built for demanding warehouse operations. These 16x14x10 kraft corrugated boxes deliver superior protection and stacking performance for mid-sized freight. Ships flat in bundles of 15 to maximize storage efficiency and reduce logistics costs.
Boxes - Corrugated

16x14x10 Double Wall Corrugated Box ECT-48 Kraft - Bundle of 15

PN: HD161410DW

16 x 14 x 10 in D.W./ECT-48 Corrugated 15 PER BUNDLE
$84.99 / BUNDLE
IN STOCK Heavy-duty 15x15x15 corrugated boxes engineered for maximum stacking strength and freight efficiency. ECT-44 single wall kraft construction delivers 40% greater protection than standard shipping cartons. Sold flat in convenient bundles of 25.
Boxes - Corrugated

15x15x15 Heavy-Duty ECT-44 Kraft Corrugated Boxes - 40% Stronger, Bundle of 25

PN: HD151515

15 x 15 x 15 in ECT-44 Single Wall Corrugated 25 PER BUNDLE
$147.57 / BUNDLE
IN STOCK Industrial-grade ECT-48 double wall corrugated boxes engineered for heavy-duty shipping and storage. 15x15x10 kraft cartons with superior stacking strength and crush resistance. Ships flat in bundles of 15–maximize warehouse efficiency and reduce freight spend.
Boxes - Corrugated

15x15x10 ECT-48 Double Wall Corrugated Boxes - Heavy Duty Shipping, Bundle of 15

PN: HD151510DW

15 x 15 x 10 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$95.88 / BUNDLE
IN STOCK ECT-48 double wall construction delivers superior crushing strength and stacking performance for demanding fulfillment operations. These 15x15x15 kraft corrugated boxes ship flat in bundles of 15, reducing warehouse footprint and freight costs by up to 40% versus assembled cartons. Ideal for mid-weight products, e-commerce fulfillment, and high-volume distribution.
Boxes - Corrugated

15x15x15 ECT-48 Double Wall Corrugated Boxes - Heavy Duty Shipping, Bundle of 15

PN: HD1515DW

15 x 15 x 15 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$65.16 / BUNDLE
IN STOCK ECT-48 double wall corrugated boxes engineered for maximum stacking strength and freight protection. These 12x12x18 kraft cartons arrive flat-packed to reduce warehouse storage footprint and shipping costs. Bundle of 15 units–the industrial standard for mid-size shipments.
Boxes - Corrugated

12x12x18 ECT-48 Double Wall Shipping Boxes - Heavy-Duty Protection, Bundle of 15

PN: HD121218DW

12 x 12 x 18 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$83.49 / BUNDLE
IN STOCK 40% stronger than standard shipping containers, these ECT-44 single wall kraft corrugated boxes deliver superior stacking performance and freight efficiency for your warehouse. 16x16x16 dimensions fit standard pallet configurations and maximize cube utilization. Sold flat in bundles of 25 for cost-effective bulk purchasing and easy storage.
Boxes - Corrugated

16x16x16 ECT-44 Heavy-Duty Corrugated Boxes - Bundle of 25

PN: HD1616

16 x 16 x 16 in ECT-44 Single Wall Corrugated 25 PER BUNDLE
$97.76 / BUNDLE
IN STOCK Industrial-grade ECT-48 double wall corrugated boxes engineered for maximum stacking strength and freight efficiency. Ships flat to minimize warehouse storage footprint–15 boxes per bundle. Kraft construction handles demanding fulfillment, storage, and shipping applications.
Boxes - Corrugated

16x16x14 ECT-48 Double Wall Boxes - Heavy Duty Kraft Cartons, Bundle of 15

PN: HD161614DW

16 x 16 x 14 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$128.19 / BUNDLE
IN STOCK Heavy-duty ECT-48 double wall corrugated boxes designed for demanding warehouse and fulfillment operations. 16x16x12 dimensions with superior stacking performance and crush resistance. Ships flat in bundles of 10 to maximize storage efficiency and reduce freight costs.
Boxes - Corrugated

16x16x12 ECT-48 Double Wall Kraft Boxes - Heavy-Duty Shipping Cartons, Bundle of 10

PN: HD161612DW

16 x 16 x 12 in ECT-48 Double Wall Corrugated 10 PER BUNDLE
$40.29 / BUNDLE
IN STOCK ECT-48 heavy-duty double wall kraft cartons engineered for maximum protection and stacking performance. 16
Boxes - Corrugated

16x16x10 ECT-48 Double Wall Corrugated Boxes - Heavy Duty Shipping, Bundle of 15

PN: HD161610DW

16 x 16 x 10 in ECT-48 Double Wall Corrugated 15 PER BUNDLE
$90.33 / BUNDLE

Product Help Request

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Overview

Heavy duty shipping boxes for freight-class weight: every box here is double wall construction or rated ECT-44, ECT-48, or ECT-51 — the grades built for stacking strength and 65–120 lb contents that standard ECT-32 singlewall can't safely carry. Kraft corrugated, sold in bundle quantities with case pricing on the product page, shipped from 5 US regional warehouses.

How to choose: ECT-44 double wall for dense products up to ~65 lb per box; ECT-48 for ~80 lb or sharp-cornered industrial parts; ECT-51 for the heaviest palletized freight. If you're replacing a 275# burst-test spec, ECT-44+ double wall is the equivalent class. Not sure which grade? See the shipping box size chart or buying guides, or ask us for a spec match.

ECT grades at a glance

Grade Construction Typical contents limit Replaces (burst-test class)
ECT-44 Heavy single wall / light double wall ~65 lb 275# single wall
ECT-48 Double wall ~80–100 lb 275# double wall
ECT-51 Double wall, heavy ~120 lb 350# class

Typical industry guidance — the certificate stamp printed on each box governs. Every product page lists the exact grade.

Frequently asked questions

What does ECT mean on a box?
ECT is the Edge Crush Test rating — how much stacking force a corrugated box wall withstands, in pounds per inch of width. Higher ECT means more stacking strength: ECT-32 is standard shipping grade, while ECT-44 through ECT-51 are heavy-duty grades for dense or palletized loads.

What is the difference between single wall and double wall boxes?
Double wall boxes have two fluted corrugated layers between three liners instead of one, roughly doubling stacking strength and puncture resistance. They hold their shape under heavy contents and pallet stacking where single wall would bulge or crush.

What replaces a 275 lb test box?
As a rule of thumb, 275# burst-test single wall corresponds to about ECT-44, and 275# double wall to about ECT-48. When replacing a specified box, match the certificate stamp class rather than the nominal name.

Do heavy duty boxes cost more to ship?
They weigh slightly more per box, but carriers price mostly on total shipment weight and dimensions. Packrift shows live carrier-quoted freight at checkout from 5 US regional warehouses, so you see the real landed cost before ordering.

Updated August 1, 2026. Grades and counts refresh automatically as catalog stock changes.

Looking for sturdy shipping boxes that hold up under real freight? Every grade here is rated for exactly that — the ECT stamp tells you how sturdy, in numbers instead of adjectives.

Buying path

Buy Heavy Duty Shipping Boxes (Double Wall, ECT-44 to ECT-51) by the specs that change the order

Use filters, product titles, and product pages to compare size, material, pack count, case quantity, and fit before ordering.

Compare

Use filters and product titles to narrow by the specs that affect fit.

Confirm

Open the product page before ordering a case so you can check quantity, unit, and limits.

Reorder

Save the SKU or product link for repeat purchasing and support questions.

Larger orders

For pallet, recurring, or mixed-SKU needs, send support the details before placing a large order.

What to check first

  • Inside dimensions
  • Board grade or strength rating
  • Box style and closure
  • Case or bundle quantity
Common wrong-order risk: Choosing the outside size instead of the inside size. Confirm product fit, void fill, and storage space before ordering.
Use the box size calculator -> Contact support for larger orders -> Compare corrugated box types -> View products below ->