Sell Shipping Boxes Wholesale by the Spec, the Bundle and the Quote

The style has a number. The Fibre Box Association says many standard box styles "can be identified in three ways: by a descriptive name, by an acronym based on that name, or by an international code number." That code system, the International Fibreboard Case Code, was developed by the European Federation of Corrugated Board Manufacturers (FEFCO) together with ESBO. The everyday shipper is 0201, the Regular Slotted Container, or RSC. The National Motor Freight Classification defines an RSC as a box where "all flaps are the same length, but the two outer flaps meet in the center of the box when folded."

The size has an order. In the NMFC fiberboard box items the Fibre Box Association republishes, length is "The larger of the two dimensions of the open face," width is "The lesser of the two dimensions of the open face," and depth is "The distance between the innermost surfaces of the box measured perpendicular to the length and width." Under those definitions, 12 x 10 x 8 and 10 x 8 x 12 are different boxes. The first opens on its 12 by 10 face, the second on its 10 by 8 face. A search bar that reads the three numbers as loose keywords returns both.

The board has a flute and a wall count. The Fibre Box Association gives A flute about 33 flutes per foot, B flute about 47, C flute about 38, E flute about 90 and F flute about 125. Single wall is a corrugated medium "glued between two sheets of linerboard." Double wall is "Three sheets of linerboard with two mediums in between," and triple wall is "Four sheets of linerboard with three mediums in between." The association adds that "larger flute profiles deliver greater cushioning and vertical compression strength, while smaller flute profiles provide enhanced graphics capabilities." So the flute is a print decision as well as a strength decision.

Two tests, two certificate forms. Under NMFC Item 222-1, fiber boxes made to its specifications "must bear a legible certificate of a box manufacturer on an outside surface, guaranteeing that boxes do so conform." The item has one certificate form for boxes made to "the burst or puncture test" and another for boxes made to "the edge crush test." Bursting strength is measured "in pounds per square inch as determined by the Mullen Tester." The edge crush test measures resistance to compression "as pounds per inch of width."

Two numbers, two units. A box spec written as "200#/ECT-32" carries both: a bursting test in pounds per square inch and an edge crush value in pounds per inch of width. A catalog that stores "200#/ECT-32" as one line of text cannot filter on either number.

The weakest part sets the rating. For boxes with more than one fiberboard component in the outside container, the NMFC says the certificate "must reflect the lowest represented bursting test or edge crush test of any given part." And not every box carries the circle. In its note on nonconforming boxes, the NMFC says boxes may bear the circular certificate "only when the provisions of Item 222 have been met," and that nonconforming boxes "may bear a straight line stamp indicating the box manufacturer and the test of the fiberboard on a voluntary basis." Which mark a box carries belongs on its product record.

The weight limit is on the bottom flap. UPS's packaging tips tell shippers not to exceed "the maximum weight limit for the box (weight limits appear on the bottom flap)." UPS's packaging guidelines (November 2024 edition) say that limit "is printed on the Box Maker's Certificate on the bottom flap of most boxes." The Box Strength Guidelines chart in that edition lists, for a weight of 0 to 30 lbs, a 200 lb bursting test or a 32 lb per inch edge crush test in single wall. For 31 to 50 lbs it lists 250 and 44, and for 81 to 100 lbs it lists 350 and 61 in double wall. UPS adds that these strengths "are only guidelines" and "are not to be considered packaging specifications." A buyer packing a 40 lb product is shopping for a test value before a size.

Dimensional weight rewards the box that fits. The FedEx How to Pack guide says "Dimensional weight applies when the package is relatively light compared with its volume," and "Your chargeable weight is the greater of the actual weight or the dimensional weight." One packaging distributor sells multi-depth cartons, "scored at intervals at the sides of the box," to "Minimize the impact of dimensional weight pricing." For an ecommerce seller, the box choice is also a freight bill.

Thousands of stock sizes, then custom work. One national packaging distributor's corrugated box page opens with "OVER 1,700 BOX SIZES IN STOCK." The Fibre Box Association notes that corrugated boxes "can be custom designed to meet the specific needs of any box user." A custom box starts as a conversation about style, size, board and print, and that conversation needs a home other than an inbox.

Spec attributes, not product titles. Style and its code, inside length, width and depth, flute, wall, test type and test value become separate, filterable attributes, built during implementation from your item master. A buyer can narrow to single wall, 32 ECT, inside depth between 6 and 8 inches, and see only those boxes. Length, width and depth keep the NMFC order, so a 12 x 10 x 8 never shows up for a 10 x 8 x 12 search.

A fits-inside finder. The buyer enters the product's dimensions and sees the boxes whose inside dimensions clear them, smallest first, so the box that fits is also the one that keeps dimensional weight down. That finder is built during implementation from your size table.

Certificate data on the product page. Test type, rated value and whether the box carries the circular certificate or a straight line stamp are shown as product attributes from your plant's data, configured during implementation. Uncap does not test or certify boxes. The storefront shows what your plant has certified.

Proof, labeled at its true distance. Uncap has not published a corrugated or packaging case study. The closest build is ULE Group, which describes itself as "a national leader in electrical, lighting, and power distribution solutions," with a catalog of over 250,000 SKUs on Shopify B2B. Its product data is managed in a PIM, search runs on Algolia with more than 100 filters, and a cart-level convert-to-quote feature handles high-value purchases. Custom functionality suggests alternative products when items are out of stock, and Epicor sends real-time product, inventory and pricing updates. The filter architecture, the quote at the cart and the alternative when a size is out are the transferable parts. Applying the alternatives logic to box sizes is built during implementation.

Bundles enforced at checkout. Shopify B2B catalogs carry quantity rules, and Shopify's own example could have been written for this trade: "if your products are boxed in multiples of 10, then you can set your increment rule to 10 so customers must purchase 10, 20, 30, products at a time." A box sold in bundles of 25 gets an increment of 25. Increment rules apply to product variants, and quantity rules "are re-validated in checkout." Volume pricing "lets you offer additional price breaks to customers when they purchase larger quantities of a product in a single order," with up to 10 price breaks per product.

Custom print quotes in Uncap Quotes. Uncap Quotes applies negotiated prices, tiers and volume breaks automatically, sends exceptions to the right approver and generates clean, shareable quote documents. Quotes carry validity windows and a full revision history, and approved quotes turn straight into Shopify orders. The custom box fields (style, inside dimensions, flute, wall, test, print colors and quantity breaks) are built during implementation as the quote's configuration rules.

Reorders in Uncap Portal. In Uncap Portal, each buyer sees their assortment and pricing, so a box printed with one customer's logo appears only in that customer's account. Reorder lists and order history are a click away. Accounts are real multi-user accounts with roles and permissions, with budgets, approvals and limits per user, and NET terms, invoices and payments sit in the portal.

The ERP stays the system of record. Uncap Connect is the real-time data layer between Shopify and your ERP: inventory, orders, customers and pricing move the moment they change, not in an overnight batch. It starts at $8,000 for onboarding and then a flat $390 per month. Field-level rules decide which system wins, every time, and failed sync events are isolated, surfaced in a live console and replayable, so nothing is silently dropped. Connect has native support for Shopify B2B companies, locations, catalogs, price lists and payment terms, and mapping one customer's printed box SKU from the ERP to that customer's catalog is configured during implementation. Integration can also run as a managed iPaaS integration. For made-to-order custom boxes, showing a ship date in place of a stock count is built during implementation from your ERP.

• Spec filters. Style, inside length, width and depth, flute, wall, test type and test value as separate attributes, built during implementation from your item master.
• Fits-inside finder. Product dimensions in, boxes that clear them out, smallest first, built during implementation.
• Certificate attributes. Test type, rated value and certificate or stamp shown from your plant's data, configured during implementation.
• Bundle increments. Shopify quantity rules for minimums and increments, with volume pricing for price breaks.
• Custom box quotes. Uncap Quotes with approvals, validity windows, revision history and one-click conversion to an order, with the box configuration rules built during implementation.
• Customer-only printed SKUs. Each buyer sees their assortment and pricing in Uncap Portal, with reorder lists and order history.
• Out-of-stock alternatives. The next box that fits suggested when a size is out, built during implementation on the pattern used at ULE Group.
• ERP sync, Connect or managed iPaaS. Inventory, orders, customers and pricing kept current between Shopify and the ERP.

The line between product and build, in writing. Quoting and approvals ship in Uncap Quotes, trade accounts and reorders in Uncap Portal, and ERP sync in Uncap Connect. Spec filters, the fits-inside finder, certificate attributes, the box configuration rules and size alternatives are built during implementation from your data. The scope says which is which.

Credentials you can check. Uncap is a Shopify Platinum Partner.

Scoped before it is built. The Uncap Blueprint is a $7,500 fixed-price, 4-week Shopify migration plan. It covers solution architecture, a data migration taxonomy, an ERP integration audit, UX and flow prototyping and a replatforming risk register, and the fee is credited 1:1 toward implementation. For a box maker or distributor, that architecture work can cover the spec attribute model, the custom quote fields and the ERP integration. You walk with everything you need to brief any agency or your in-house team.

This page sits under packaging and shipping supplies ecommerce, which covers each, inner, case and pallet pricing, break pack rules, contract pricing from the ERP and freight rated as freight. This page goes down to the corrugated box itself: its style code, inside dimensions, board and certificate. For distributors selling boxes alongside a broader consumables catalog, see industrial supply and MRO. For the ordering rules, see the glossary entries for case pack and MOQ, and the guide to order minimums, case packs and MOQs on Shopify. For the ERP side, see the Epicor Kinetic integration or the full list of ERP integrations.

Bring two documents. The first is your stock box size list with style, inside dimensions, flute, wall and test for each item. The second is the last custom print quote your team sent by email. Together they show how much of your catalog is data and how much of your selling still runs through a rep.

Talk to Our Experts about your box catalog, or start with a Blueprint if what you need first is the spec model, the quote fields and the ERP integration written down and costed.