Replacement plastic housing from a pair of type 1 GHD 4.2B. This is the switch side arm which the cable connects to in a matt black colour.

This arm has PCB mounting hole 21mm apart 

Please note that there are a number of different variations of 4.2B case work so you need to check compatibility carefully. This arm is a type 1 arm as shown on the 4.2B page.

This part is a 2nd hand and has been removed from a broken pair of GHDs.