PBV Part 4: What information do I need to have to get a quote from China – Part 3 – BOM and Specifications


Manufacturing in China – Pulling Back the Veil, Part 4

This is Part 4 of a 10 part series called “Pulling Back the Veil” that aims to answer the basic question “how do I manufacture my product in China”? These articles are primarily step-by-step instructions and directly applicable information about manufacturing in China. To see the other “Pulling Back the Veil” Articles, click the “Pulling Back the Veil Link” under the categories section to the right.

So, you’ve worked hard, you’ve created some solid drawings with an engineer, you have a beautiful prototype. You’re ready to go, right? WRONG! The most important part of the development process seems to always get the least attention. In order to know what you going to be making in the factory exactly, you must specify exactly what you want to make. The drawings and prototype can go a long way towards this goal, but these will still always leave out information. To complement them, you need a set of clearly listed specifications.  The best way to start with creating specifications is to make your Bill Of Materials (BOM).

Bill Of Materials


A BOM is simply a document that lists all of the materials/components, separately, in a product. That is simple enough. Here is a sample BOM.  The columns you use in your BOM will vary depending on how you would like to describe your components, but should at least include the quantity/product, the part name, part description, and material.


every specification should have a tolerance
Once you have the BOM, each component should have its own set of specifications. Since each product has a huge spectrum of possibilities regarding the specifications, it’s difficult to list them all out here. You must think about it. It is not a simple task. A few that generally reoccur though are:

1) Materials (what is the component made of)

a. Plastic is not a material. 100% recycled PU is closer, but still leaves some ambiguity. Try to be as specific as you can. The factory can only make what you ask it to make for you, and if there is any ambiguity and one costs more than the other, guess which one the factory will choose?

 2) Dimensions

a. These should be in the drawings. Make sure that tolerances for every dimension are specified. There is not a piece of paper on earth that is exactly 8.5”x11” (ie. 8.50000000000000000…” x 11.0000000000000000…”). Let the factory know what is acceptable. When starting out, a person new to the business will tend toward higher quality, but remember that a small change in what is acceptable can mean a totally different (and much more costly)
Diameter Measurement

Getting the dimensions right

manufacturing process. So, try to stick with what will be acceptable to your customers, and what is easy to make for the factories. Your price point will thank you for it.

b. A corollary to this is that no mass product can be made exactly like a prototype. As mentioned in the last post, the manufacturing processes between a prototype and a mass product will usually be different, so some features can be hard to mimic (though often they will actually be better). If you want something similar to your prototype, then base your specifications on your prototype, but leave room for manufacturing variance. Understand the details of what makes your prototype like it is and define those in quantitative terms.

3) Surfaces

a. Are they chrome, fuzzy, textured, matte, glossy…? Usually surfaces have a lot of detail and most of the time there are common quantitative ways to express those. For example, there is a book of textures for plastics that most designers will have. You can take a look at this and use it to describe the kind of texture you want very precisely. There are similar tools for the others. Talk to those in the business to find out what tools can be used to describe the surface you are looking for exactly. Your idea of “very glossy” may be much different than someone else’s. Don’t leave that up to chance.

4) Color

a. There are thousands of kinds of red. Use a pantone number to define exactly what color you are looking at. Color on every computer screen is different, so do not use pictures on a screen as a reference. Also, if you are describing color for a product like silicone, it can be very difficult to match with a color on a pantone book as the materials are so different, the light disperses off the surface differently and to some it can look different than to others. When working with a material like this (with different light interaction than the pantone book), try to make a sample of the color you want in the correct material for the factory’s reference.

Product as a Whole

Besides the specifications for each component, you should also have separate specifications about the product as a whole. Just defining the components doesn’t always clearly define what the total product will be like. Some things to consider:

1) How will the components fit together? Are there any special requirements?
2) What should be the overall functional requirements? These are often just the marketing features of your product (i.e. can function 30 ft. underwater, battery life of 10k hours…)
3) Shipping requirements? Do you want the product palletized?
4) Is there anything it shouldn’t have? Non-recycled materials, heavy metals….?
5) Are there any global requirements it must meet (UL, CE, FDA…)?
6) Safety requirements? Should it not get hotter than a certain temperature, will kids be putting it in their mouths…?

The specifications are critical for a number of reasons. Besides just letting the factory know what you want, they are also the foundation of your business contract and quality control initiatives. Every specification is the benchmark for making each inspection guideline. This is a good frame of reference to think about when writing them. When written well, each specification will make it obvious how to test it and the tolerance allowable. The format of the specifications is not as important, just that they are communicated well and measurable.


Reminder: every specification should have a tolerance. It isn’t possible for a factory to make a metal piece with an exact Rockwell hardness of 67. There must be some room for manufacturing variance. If you don’t specify your expected variance, then the factory will use their own assumptions (most likely to your detriment). If you can accept 67 +/-1 , you must let them know. Accepting 67+/-2 might make your product easier/cheaper to produce. Every specification must have a tolerance, nothing in this world is exactly perfect. Expecting the impossible will only result in disappointment.

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