What term describes a non-standard part that is made specifically to fit a particular application?

A non-standard part that is made specifically to fit a particular application is best described as a custom part. Custom parts are designed and manufactured to meet very specific requirements or specifications of a project, which may include unique shapes, sizes, or materials that are not available in standard parts. This allows for tailored solutions to meet the needs of diverse applications in welding and manufacturing processes.

Prototype refers to an initial model that is used to test concepts and design before mass production; while it may also be unique, it is not the same as a custom part intended for final use. Standard parts are those that are widely available and conform to specifications, making them interchangeable in various applications. Mass-produced parts are manufactured in large quantities to serve broad applications, lacking the specificity associated with custom parts. Thus, custom part is the most accurate term to describe a non-standard part tailored for a specific application.