Custom servoamplifiers were usually used in areas requiring specific form, fit, and function. Today, limiting costs by removing unwanted or unnecessary features plays a bigger role in determining the choice of amplifier.

Form: The packaging and dimensions Fit: The fit of how the product fits into the overall machine system. A prime example is communications: Does the product have communications capabilities that enable it to merge easily into the system?

Function: What activity the product performs. Some examples are the control structures employed in the product, or the protection and diagnostic functions offered.