Optical subsystems exist in a wide variety of configurations for a whole range of applications. Most of the parts that go into such optomechanical assemblies — laser and LED light sources, lenses, dichroics, filaments, detectors, spatial light modulators, and all the associated mechanical fixtures — are available as commercial off-the-shelf (COTS) parts. So it can be tempting to say that if you’re designing a new optical subsystem, you should just purchase the parts and build it yourself. But is that really the right choice? Here are a few questions you might be asking when you’re considering whether to build your own assembly or have it custom-made by an experienced design and manufacturing team.