How to Choose a 3PL for High SKU Counts and Kitting

To choose a 3PL when you have a high SKU count or complex kitting, test the warehouse on the work you actually do: how it slots and counts thousands of items, how it builds a kit from a written work instruction, and how it bills for both. Ask for a pilot on your real orders before you sign. A low rate card tells you very little about either.

Most 3PLs quote well on a clean catalog of 50 SKUs shipping single units. Add 800 SKUs, or a kit with seven components from four vendors, and the quote hides most of the work. This guide covers what changes, what to look for, how pricing shifts, and how to test a provider. For the full scoring method, see How to Score 3PL Proposals So You're Comparing Apples to Apples.

Why do high SKU counts and kitting change how you choose a 3PL?

High SKU counts and kitting move the cost and risk from the rate card to the warehouse floor. More SKUs mean more pick locations, more receiving errors, and more cycle counting. Kitting adds assembly labor, component inventory, and a second set of records to keep accurate. A 3PL that is strong on simple DTC orders can still struggle with both.

These are two different problems, and many brands have only one. A broad catalog stresses receiving, slotting, and inventory accuracy. Kitting stresses labor, quality control, and system setup. Providers are usually built for a catalog band, such as under 100 active SKUs or over 1,000, so the first question is whether your catalog sits inside the range a provider handles today.

The second question is what counts as kitting in the first place. In an Izba engagement that moved kitting from a failed 3PL to a new US facility in 90 days, the team reconciled a 134-item list across 7 categories and found only 55 items belonged at the new site. Vendors kept assembly for the rest, and the 3PL handled true kitting. Separating the two before you pick or scope a 3PL keeps you from paying warehouse labor rates for work a factory already does.

What should a 3PL have for a high SKU count?

Look for a WMS that tracks location, lot, and size at the SKU level, a slotting plan that puts fast movers near packing, routine cycle counts, and receiving that checks every unit against the ASN. Ask for inventory accuracy history and how the team runs a catalog of your size today.

Here is what to check:

• Receiving and unit of measure. Receiving discrepancies often come from small unit mismatches, such as eaches against cases. Ask how the 3PL confirms case counts and pallet information per SKU on arrival.
• Catalog setup. Brands map the catalog before launch: renamed or consolidated SKUs, case counts, weights, and dimensions. Ask who does this work and how long it takes for a catalog your size.
• Slotting and pick paths. Median picks per order matter more than total orders. Two bids on the same 6,000 orders can differ widely if one slots your top 50 SKUs near packing and the other does not.
• Cycle counting. Ask how often counts run and what accuracy rate the team reports. Counting thousands of locations takes planned labor.
• Size-level tracking. Apparel and footwear need barcode tracking by size, including mixed-size cartons that arrive floor-loaded.
• Long-tail inventory. You pay storage on every slow SKU. Izba's SKU rationalization approach flags inventory above six months of demand, and extra attention goes to stock aged over 180 days. Clean up the tail before you transition, and the quote gets smaller.

For a phased approach on a SKU-heavy catalog, move styles in groups rather than all at once. A catalog of about 300 SKUs across 50 styles is easier to cut over in waves than in a single weekend.

What should a 3PL have for complex kitting?

Ask whether the 3PL does true kitting: written work instructions, first-article approval, component control, and a kit-level SKU in the WMS. Ask to see photos of a kit built on site. Confirm lot tracking if your components carry lots, and settle who owns assembly and who owns kitting.

Kitting comes in two main forms. Pre-built kitting assembles kits ahead of orders from a forecast. On-demand kitting assembles them during fulfillment. Either way, the 3PL needs SKU mapping, inventory sync, order routing, and returns handling for the kit and for its parts.

Service levels vary. Some providers only relabel or apply stickers. Others handle simple DTC assembly, retail display assembly, or gift wrapping. Match the provider's actual service list to your kit, and ask for a reference with the same kit type.

Check these items before you commit:

• Work instructions. In the Izba kitting move, the team wrote 63 work instructions across 9 kit families and 13 countries and regions. A 3PL without a documented instruction for each kit will rely on memory, and memory fails at volume.
• First articles. Have operators build the first kit of each family while you watch, or review photos. The Izba team ran first articles with operators during two site visits before launch.
• Lot tracking. If part of your outbound units are lot tracked, confirm the WMS carries lots through the kit, not only on the components.
• Virtual bundles. If a bundle is only a listing on your storefront, the WMS can map its components into a pick list. No assembly is needed. Use physical kitting only when the product must be assembled or packaged together.
• Retail kits. Retail kitting often brings EDI, ASN generation, and chargeback exposure. See 3PL retail compliance before you scope retail kits.
• Phasing. Launch priority kits first and add the rest in a second wave. The Izba move delivered 13 priority kits first, then the remainder, with zero stock-outs.
• ERP match. If your ERP builds kits, it needs the right lots on manufacturing orders, a bill of materials, inventory consumption, and the resulting inventory added. Ask how the 3PL reports kit builds so your records match.

How does pricing change with many SKUs or kitting?

Pricing shifts from a flat per-order rate to per-kit, per-pick, and per-component charges. Many SKUs raise storage and receiving fees, and kits add assembly labor billed apart from standard pick and pack. Model your real kit and order mix on every quote, then compare total landed cost instead of rate cards.

Expect these line items: a per-kit fee or kitting labor rate, a pick fee for each component, receiving fees by pallet or carton, and a monthly minimum. Most cost models take the larger of your charges and the monthly minimum, so a small catalog launch can cost more than the volume suggests. Special packaging, such as a holiday bundle, is often a flat charge billed apart from standard pick and pack.

Here is an illustrative example. A kit has six components. The 3PL charges $2.75 per order plus $0.45 for each additional pick. The five additional picks add $2.25, so the pick and pack charge is $5.00 before any per-kit fee. Another bid charges $1.15 per unit plus $1.00 per order. The same kit costs $7.90. Compare both on your kit mix, not on a single-unit order. (These figures are illustrative.)

Kitting invoices usually arrive at month end, so finance teams estimate a landed kitting cost per unit and true it up later. Ask each bidder for a sample invoice that shows kit lines. To normalize the bids, use the steps in how to read a 3PL pick and pack quote, watch for hidden 3PL fees, and roll everything into total landed cost. The cost comparison example shows the math on three bids.

How do you test a 3PL before you commit?

Send each finalist your real catalog and your hardest orders, then ask for a pilot or sample build. Check references with a similar SKU count or kit type. Score every answer on the same weighted scorecard. A provider that cannot show a built kit or a count history is guessing.

Put these questions to every finalist:

1. How many active SKUs does your largest client run, and how many does this building hold today?
2. Which WMS do you use, and how does it handle kits, lots, and size-level inventory?
3. Can I see a work instruction and photos of a kit you built for another client?
4. How do you reconcile received quantities against the ASN?
5. What is your inventory accuracy rate, and how often do you cycle count?
6. How do you bill for kitting, and can I see a sample invoice?

For more, see questions to ask a 3PL. Call two references with a similar catalog or kit type, and ask what went wrong in the first 90 days. A kitting fee review belongs in the 3PL's regular performance review, too, so agree on that up front. Then carry the answers into the 3PL scorecard so cost, capability, service level, and fit each get a weight. If the answers raise doubts, signs of a poor 3PL fit and signs you have outgrown your 3PL will help you decide.

Slotted structures your SKU counts, kit requirements, and lot tracking needs so every provider quotes the same job, and it shows where bids don't match. You make the call on which provider fits. Start your RFP on Slotted.

Frequently asked questions

How many SKUs is too many for a 3PL?

No fixed number applies. Providers are built for catalog bands, and a warehouse that runs 100 active SKUs well may struggle at 1,000. Ask each provider for its largest client's SKU count, its WMS, and its inventory accuracy history. Clean up slow stock above six months of demand before you quote.

What is the difference between kitting and bundling?

Kitting assembles several products into one packaged unit before fulfillment. Bundling groups products at the time of the order, often as a virtual bundle that maps to a pick list. Kitting needs assembly labor and a kit-level SKU. Bundling usually needs only correct SKU mapping in the WMS.

How much does 3PL kitting cost?

Kitting cost varies by provider, kit complexity, and volume. Expect a per-kit fee or labor rate plus a pick fee for each component, and a possible monthly minimum. Ask for build time per kit and a sample invoice, then compare total landed cost per kit across bids.

Should my 3PL or my vendors do kitting?

It depends on where assembly makes sense. Vendors often do factory-specific assembly better and cheaper. A 3PL fits when components arrive separately or kits change by channel or season. Reconcile your item list first, and scope the 3PL only for the work that belongs in the warehouse.