05 · Bottom Units & Construction
Weeks 4–5 · 25 hours
Objective
Choose a construction method and a specific sole unit you can actually afford, and specify it correctly. By the end of this module you should have a shortlist of three real, available sole units with mold numbers, matched lasts, MOQs and prices.
Why it matters commercially
The bottom unit is typically 30–45% of your FOB cost and 100% of your tooling risk. It is also the least changeable decision you will make. Getting this right in Week 5 is what makes the sub-$10k plan work.
Core concepts
Custom tooling: what you’re avoiding, and why
Custom sole tooling means machining an aluminium mold set. Ballpark figures for planning:
| Item | Typical cost |
|---|---|
| Custom EVA/phylon midsole mold | $400–$900 per size |
| Custom rubber outsole mold | $500–$1,200 per size |
| Custom cupsole mold (single-piece) | $700–$1,500 per size |
| A commercial size run | 15–25 sizes |
| Realistic total for a custom bottom | $12,000–$45,000 |
Plus 6–12 weeks of mold-making lead time and typically a mold trial round that finds problems. This is the wall that stops first-time brands. Treat these numbers as planning estimates and get real quotes — they vary by factory, region and complexity.
Open molds: what you’re using instead
Sole factories and soling houses maintain catalogues of existing molds — thousands of them. You pick a mold number, specify material and colour, and pay $0 tooling. You share the mold with other brands, which is the trade-off. Nobody in your market will notice or care on a first drop; the design differentiation lives in your upper, materials, proportions and brand.
What you can still customise cheaply on an open mold:
- Colour of midsole and outsole (usually free or near-free, above a minimum)
- Material and density — the same mold can be run in different rubber compounds or foam densities
- A logo insert — many molds accept a small replaceable plate in the heel or forefoot. Typically $150–$500 for an insert, not per size in some cases. Ask.
- Sidewall treatments — paint, screen print, debossing where the mold allows
Where to find open molds: soling suppliers’ catalogues (request PDFs), your factory’s in-house library, Vibram’s stock soling programme, and the sole factories clustered around Jinjiang and Dongguan in China and around Felgueiras and São João da Madeira in Portugal. See Suppliers.
The pairing rule again. A sole unit is designed around a specific last bottom. Always ask a sole supplier: “Which last is this mold built to, and can the factory that will assemble my shoe get that last?” Getting this wrong produces a shoe with a visibly bad bite line and gaps at the waist.
Reading a sole spec
A quoted sole unit should give you:
| Spec | Meaning | Typical sneaker values |
|---|---|---|
| Mold number | The supplier’s identifier. Use it in every email | — |
| Size range available | Which sizes the mold set covers | Often narrower than you want — check |
| Material | Rubber type, foam type | See below |
| Hardness (Shore A) | Rubber stiffness | Outsole 55–70 Shore A |
| Density (Asker C or g/cm³) | Foam firmness | Midsole EVA 45–60 Asker C |
| Stack height | Forefoot / heel in mm | Court 12/22mm · runner 22/32mm · chunky 30/45mm |
| Drop / offset | Heel minus forefoot | 6–12mm typical; 0 for flat/vulc |
| Weight | Grams per unit, sample size | A 300g+ bottom makes a heavy shoe |
| MOQ | Minimum per colour, per size or total | The number that decides everything |
| Price | Per pair, at MOQ | $4–14/pair typical for open-mold |
Bottom materials
Foams (midsole):
| Material | Character | Notes |
|---|---|---|
| EVA (die-cut or compression-moulded) | Light, cheap, cushions well | Compresses permanently over time (“packs out”) |
| Phylon | Compression-moulded EVA — the athletic standard | Lighter and more refined than plain EVA; the wrinkly-sidewall look |
| PU (polyurethane) | Denser, more durable, more resilient | Heavier; used in premium and work footwear; can hydrolyse over years |
| Rubber wedge | Firm, retro, no cushioning | Vulcanized and heritage looks |
| Supercritical foams / TPU-based | Modern high-rebound | Expensive, mostly proprietary to big brands. Not your first shoe |
Rubbers (outsole):
| Material | Character |
|---|---|
| Natural gum rubber | Warm honey colour, excellent grip, marks and yellows |
| Carbon rubber | Carbon-black filled; hard-wearing, black, the durability default |
| Blown rubber | Foamed rubber; lighter, softer, less durable |
| Translucent / “ice” rubber | Clear; looks great, yellows with UV over time — a known and accepted trait |
| Recycled-content rubber | Increasingly available; verify content claims with documentation |
Choosing your construction, decided
Given a sub-$10k budget, your realistic options and their profiles:
| Vulcanized | Cemented + open-mold cupsole | Cemented + open-mold phylon/EVA | |
|---|---|---|---|
| Tooling | $0–300 | $0 | $0 |
| Typical FOB | $18–30 | $26–45 | $24–42 |
| MOQ (China) | 300–600/colour | 300–600/colour | 300–600/colour |
| MOQ (Portugal) | 100–300 | 100–300 | 150–300 |
| Look | Flat, heritage, skate | Court, luxury-minimal, skate | Athletic, retro-runner, chunky |
| Comfort | Low | Medium | High |
| Factory availability | Fewer factories | Many | Many |
| Risk for you | Oven-dependent; fewer partners | Bite line must be perfect or it looks cheap | Sidewall finish quality varies a lot |
There is no wrong answer here. There is only the answer that matches the design you want to make and the factory you can actually get.
MOQ reality and how to get under it
Minimums are quoted per colour, and sometimes separately for the sole and the upper materials. The real minimum is usually set by whichever component has the highest one — often the sole or a specialty material.
Legitimate ways to lower your first order:
- One colourway. Halves or thirds your minimum immediately.
- Truncated size run. US 7–12 whole sizes only = 6 sizes.
- Use only materials the factory already stocks. Their existing inventory has no minimum for you.
- Ask for a “trial order” or “first order” exception. Many factories will accept 100–200 pairs once, at a higher per-pair price, to start a relationship. This is normal. Ask directly and accept the price penalty.
- Portugal / Spain over China if your minimum problem is worse than your price problem.
- An agent or sourcing consolidator who bundles small brands’ orders. Costs 5–15% commission, and can be worth every cent for a first run.
Do this
1 · Catalogue study (5h). Collect at least four open-mold sole catalogues (you started requesting these in Module 2). Build a comparison spreadsheet of every unit that could plausibly work: mold number, supplier, stack, drop, materials, size range, MOQ, price, matched last.
2 · Construction decision memo (4h). Write a one-page memo choosing your construction family. State the design you want, the three constructions considered, the cost and MOQ implications, and why you chose what you chose. Put it in your build log. You will refer back to this when a factory tries to talk you into something else.
3 · Stack measurement (3h). From your dissected shoes plus five shoes in a store, measure and record forefoot stack, heel stack and drop. Build an intuition for what 8mm of drop looks like versus 12mm.
4 · Sole shortlist (6h). Narrow to three specific sole units with mold numbers. For each, email the supplier or factory and get: confirmed price at 200 and at 500 pairs, MOQ, size range, matched last availability, lead time, and whether a logo insert is possible and what it costs.
5 · Sample soles (3h). Ask your top two suppliers to courier you a physical sample pair of the sole units. Many will, free or for the cost of shipping. Holding the actual object changes decisions.
6 · Outreach block (4h). Continue.
Deliverable. A sole comparison spreadsheet; a signed-and-dated construction decision memo; and three shortlisted sole units with real quotes attached, including matched-last confirmation.
Self-check
- Why does custom tooling cost so much, and what’s a realistic total?
- What can you still customise on an open mold, and what does it cost?
- What’s the difference between EVA and phylon? Between gum and carbon rubber?
- What does Shore A measure, and what’s a normal outsole value?
- Give four legitimate ways to get a factory below its stated MOQ.
- What is drop, and what’s typical for a court shoe versus a runner?
Traps
Choosing a sole from a photo. Photos flatter soles. Get the physical unit.
Ignoring the size range. Many open molds exist only in a narrow set of sizes, or the mold set is incomplete because the original owner only ran certain sizes. Confirm every size you intend to sell exists before you design around it.
Falling for translucent rubber without disclosing yellowing. It will yellow with UV. That’s inherent, not a defect. If you use it, say so on the product page — it turns a complaint into a known characteristic.
Forgetting weight. Add up your bottom weight early. A beautiful shoe that weighs 600g per side gets returned.