When choosing between an off-the-shelf part and a custom part, which should generally be used?

• A. OTS
• B. Custom Part
• C. In-house Fabrication
• D. Prototype Only

Answer: (A)

When a standard component can meet the requirements, use off-the-shelf parts. They’re designed for broad use, so they typically cost less, ship faster, and come with built-in quality assurance and warranties. Because they’re common, you get easier sourcing, more reliable supply chains, and straightforward maintenance or replacements, which reduces risk in both development and production.

Custom parts are reserved for when standard items can’t fit the need—due to unique dimensions, critical tolerances, special materials, environmental requirements, or specific integration with other systems. In those cases, you trade higher cost, longer lead times, and greater development risk for a fit that standard parts can’t provide. So, the default choice is off-the-shelf, with custom only when the standard solution truly won’t work.