Many rapid prototyping services make their models out of material that may be strong and durable as long as the prototype is left unmodified, but fall to pieces if you attempt to alter them using tools. If you try to tap or drill your product, the vibrations usually cause the model to crack or flake apart and become useless.
The process by which we create our prototypes using nylon 12-equivalent material is sophisticated enough that the thousands of layers creating your product are bonded together in a manner that is final, meaning the model won’t flake or crack if you drill into it. The material is also flexible enough that vibrations created by tools move through the particles in a wave, leaving the product unharmed once the modification is finished. This enables you to alter your prototype and continue to test it if you discover a problem that can be easily fixed by such modification, saving you the time and money of having to order a slightly different model.