Stock Mould or Custom Mould? The Decision, Not the Definition
What each route costs you in tooling, minimum quantity, exclusivity and time — and how to search 2,000+ existing moulds before anyone quotes you a tool.
Most projects should start on a stock mould. A custom mould is for a shape or an exclusivity requirement, not for a better bottle
A stock mould already exists, so it can run at MOQ from 5,000 pieces with no tooling charge and with sampling typically inside 3–10 days. A custom mould is built to your drawing or sample, which is what a genuinely new shape, a branded profile or an exclusivity requirement needs.
The decision is not about quality. A stock cavity and a private cavity are cut and run by the same people on the same machines. It is about whether an existing cavity can give you the shape you need, and whether you need that shape to be unavailable to anyone else.
This guide is the decision framework: how to choose, what to compute and what to put in writing. The engineering sequence behind a tool — drawing review, design-for-manufacture feedback, mould build, T1 first article and handover — is on tooling and moulds.
Eight dimensions, side by side
The two routes differ on eight things that matter commercially. Read the row that your programme is most sensitive to, and start there.
| Dimension | Stock mould | Private mould |
|---|---|---|
| Tooling charge | None for the bottle. Decoration may still carry print tooling. | A tooling charge, quoted and invoiced separately from the unit price, with the cavity count stated. |
| Minimum order | From 5,000 pieces per SKU. Smaller trial volumes are sometimes possible with a start-up fee. | Set by the tooling economics and quoted per project, because the tool has to be paid for by the run. |
| Sampling speed | Typically 3–10 days, because there is no tool to make first. | A longer programme: the tool is designed, cut and trialled before the first sample exists. |
| Design freedom | Whatever the existing cavity geometry is, plus colour, decoration and closure. | Your geometry — capacity, section, shoulder, base, and any feature that has to be moulded. |
| Exclusivity | The same cavity may run for other customers, including in other colours. | Built and held in-house for your programme, not resold or reused for another customer. |
| Unit cost | Lower, because there is no tooling to amortise — until the volume is large enough for amortisation to change the answer. | Higher unit cost on a small run; on a long run the amortised tooling can make the unit cost competitive. |
| Reorder stability | Geometry is fixed, so a reorder matches. Colour and decoration still have to be held against the approved standard. | Geometry is fixed to your tool, so reorders match by construction. |
| Time to market | The fastest route, because nothing has to be cut first. | The slowest route, and the one most exposed to design changes arriving late. |
Two rows decide most programmes: minimum order and time to market. If both are tight, the stock library is the answer, and the question becomes how close a stock shape can get.
Three terms that get used loosely — and what each means in a quotation
Stock, custom and private are not synonyms, and the difference matters when the quotation arrives with a tooling line on it.
What the terms mean in a quotation
The practical difference between a modified stock mould and a private mould is what the change touches. If the geometry that carries the brand stays a standard cavity, a modification is usually enough.
How to search the existing library before you commission anything
The single most valuable thing a buyer can do at this stage is describe the requirement in the order a mould library is organised by, rather than the order a brief is usually written in.
Searching 2,000+ stock moulds
- ☐Material — the library is organised by material because the tool is cut for the material that will run in it.
- ☐Neck finish — a stock cavity either has your finish or it does not, and the neck is the highest-precision feature on the part.
- ☐Capacity as the fill volume you are designing around, not the brimful number.
- ☐Height and body diameter, if the label area and the carton allow it to move.
- ☐Section — a square or oval body holds more volume per millimetre of shelf width than a round one.
- ☐Colour, decoration and closure, which are applied after moulding and carry no tooling for the bottle.
- ☐Is the difference between the closest stock shape and your target something a customer would notice on shelf, or something only visible on a drawing?
- ☐If it is only visible on a drawing, run the stock shape and spend the tooling budget on decoration and colour instead.
If you can send a reference bottle or a photograph, we will run the search for you and tell you what is close, what is not, and what a modification would touch. It costs one enquiry and frequently saves a tool.
How to think about the break-even without inventing numbers
Break-even is a calculation you run with your own figures, not a threshold we can publish. Four inputs decide it, and only two of them are ours.
| Input | Who owns it | What it does to the answer |
|---|---|---|
| Tooling charge for the private route | Us, quoted per project and stated separately. | The more the tool costs, the longer the run has to be before a private tool wins. |
| Unit-cost difference between the two routes | Us, quoted against the same specification. | If the modified or private route does not reduce unit cost, it has to buy something else — shape or exclusivity — to be worth doing. |
| Order volume over the life of the pack | You, including the reorders you expect. | Amortisation is what changes the answer, and it is driven by the volume you actually commit to, not the volume you hope for. |
| What the shape is worth commercially | You — shelf differentiation, brand fit or channel requirement. | This is the input that is not arithmetic. Sometimes it is the only input that matters. |
A common and expensive mistake is to compute the break-even on the first order alone. Tooling is amortised over the life of the pack, and a first order that looks uneconomic can be the right answer over three reorders. The reverse is also true, which is why the volume assumption should be written down and challenged.
The threshold at which a private tool stops being worth opening, and how to test it, is worked through in when NOT to open a private mould.
Five conditions where a private mould is genuinely the right answer
If none of these is true, a stock or modified stock route will usually serve the programme better.
Custom is the right answer when
- ▸The shape carries the brand — a profile, a silhouette or a moulded feature that no stock cavity provides and that a customer would recognise on shelf.
- ▸The pack has to be unavailable to anyone else, and exclusivity is a commercial requirement rather than a preference.
- ▸The geometry is fixed by something outside packaging — a filling line, a dispenser, a carton or an existing accessory that cannot change.
- ▸The volume over the life of the pack justifies the tool, and that volume is committed rather than assumed.
- ▸The specification cannot be met by modifying a stock tool, because the change touches the geometry rather than an insert or a feature.
- ▸The only difference is colour, decoration or the closure — all of which are applied after moulding and need no new bottle tool.
- ▸The programme is a market test where the volume is not yet known.
- ▸The deadline does not allow for a tool to be designed, cut, trialled and sampled.
- ▸A stock cavity is close and the difference is visible only on a drawing.
Tooling terms: what we put in writing, and what we do not promise
Tooling terms are commercial terms, and commercial terms belong in a quotation rather than in a paragraph designed to sound reassuring. Four points are settled in writing before you commit.
What goes into the quotation
- ▸The tooling charge, quoted separately from the unit price so you can see what you are paying for and what it buys.
- ▸The cavity count, because it trades against the tooling charge and the run length.
- ▸The sampling schedule, confirmed against your geometry rather than assumed from a range.
- ▸The exclusivity position, if exclusivity is required, stated as a term rather than implied.
- ▸We do not advertise a free-mould programme.
- ▸We do not advertise lifetime mould ownership.
- ▸Any tooling charge, ownership position or transfer arrangement is confirmed in writing against your specific project rather than offered as a standing policy.
If your project depends on a tooling arrangement we cannot offer, we will tell you at quotation stage instead of discovering it after the tool is cut.
What happens after you say yes, in six stages
Tooling is the stage where a design change costs the least and a late change costs the most, so the sequence puts the reviewable decisions before the irreversible one. The engineering detail of each stage is on tooling and moulds; this is the commercial view of the same six stages.
Drawing or sample review
We start from a dimensioned drawing, a 3D file or a physical sample. A sample is often faster when the design is already fixed, because it can be measured rather than interpreted.
Design-for-manufacture feedback
Before a tool is quoted we tell you what will and will not mould reliably: blow ratio, wall distribution, undercuts, handle geometry and the features that will show sink marks. This is the cheapest moment to change the design.
Tooling quotation and schedule
The tooling charge, the cavity count and the sampling schedule are confirmed in writing, including the terms that apply to exclusivity and to ownership.
Mould build and T1 first article
The tool is designed, cut and assembled in our own mould shop, and the first shot is measured against your drawing rather than judged by eye.
Sample approval
You approve the sample. Nothing enters mass production until a physical sample has been approved for shape, colour, finish and print.
Pilot run and handover
The approved sample and the colour chip are archived as the reference for the whole programme, which is what makes a reorder comparable.
Send the requirement and we will tell you which route it needs
- ▸The capacity, material and neck finish you need, or the reference bottle you are matching.
- ▸First-order quantity and the annual volume you expect over the life of the pack.
- ▸Whether the shape has to be exclusive to you.
- ▸Your deadline, so the route is quoted against it rather than after it.
- ▸A dimensioned drawing, a 3D file or a physical sample, if one exists.
We will tell you whether a stock cavity can serve it — and if it can, that is usually the faster and cheaper answer, which is why we will say so rather than quote a tool.
Tooling, custom development and cost
Stock and custom mould questions
Do I need a custom mould to get a bottle in my own shape?+
Not always. There are 2,000+ stock moulds across PET, PE, HDPE and PETG, many of which already match common capacities and neck finishes. A stock cavity runs at MOQ from 5,000 pieces with no tooling charge, so it is normally the right place to start. A custom mould is for a shape no stock cavity provides.
What is the difference between a stock mould and a private mould?+
A stock mould is an existing cavity that may run for other customers, including in other colours. A private mould is built for one programme only, held in-house, and not resold or reused for another customer. The same cavity may also be modified for your programme, which sits between the two on both cost and time.
How do I know whether a stock mould is close enough?+
Send a reference bottle or clear images and we will measure capacity, neck finish and weight, then search the library against the fixed points first: material, neck finish and capacity. If the only difference is colour, decoration or the closure, the stock route gives you the same result with no bottle tooling.
How much does a private mould cost?+
It depends on the part, the cavity count and the material, so it is quoted per project rather than published as a price list. The tooling charge and the cavity count are stated separately from the unit price so you can see what you are paying for and what it buys.
Who owns a private mould?+
A private mould is built and held in-house for your programme and is not resold or reused for another customer. Ownership and any transfer terms are commercial terms confirmed in writing against your specific project. We do not advertise a free-mould programme or lifetime mould ownership.
Can you modify a stock mould instead of cutting a new one?+
Often, yes — a neck insert, a base change, a shoulder adjustment or a brand mark can be applied to an existing tool. It is quoted separately because it is a tooling intervention, and it normally sits between a stock run and a full private tool on both cost and schedule.
How long does a new mould take?+
A tooling schedule is confirmed against your geometry rather than assumed from a range, because the variables are whether the geometry needs rework before it can be cut, whether the neck finish is already fixed to a real closure, how quickly the sample is approved and when the machine slot is available. Sampling from an existing mould, by contrast, typically runs 3–10 days.
Can I run a market test on a stock shape and then cut a private tool?+
Yes, and it is often the cheaper route. Validating the formulation, the closure and the decoration on a stock shape costs one sampling cycle and frequently saves a tool, because by the time you cut it the artwork and the volume are already settled.
Check the library before you commission a tool
Send the capacity, material and neck finish you need, or a reference bottle. We will tell you honestly whether an existing cavity serves it — and say so if a new tool is the right answer.