'Pip Pin' is often used generically to describe ball lock pins. The term refers to a registered trade mark of a steel (4137) double acting type fastener previously manufactured by Avdel.
Quick release pins are no longer manufactured by Avdel.

The Avdel pip pin part reference of 3201 is referenced in many drawings, the pin part number being stamped onto the shoulder.

This took the form of the series number 3201 followed by a 4 digit number, the first 2 digits indicating the diameter in 1/16" and the last two indicating the grip in 1/10" - as illustrated right.

This pip pin was approved in aircraft use under SDM number 205, CAA number E1130. The SBAC/ AGS number was 2105, and was sometimes referenced as an AGS 2105-xxxx.

The Avdel Pip Pin

A piece of engineering history