Provided is a housing part for an auto-injector comprising a shell form body defining inner and outer shell surfaces and comprising a relatively hard or generally incompressible material; an over-coating formed of a relatively softer or more compressible material, the over-coating covering at least part of the outer shell surface of the shell form body; and at least one window defined in the shell form body, wherein the over-coating extends into the at least one window. Also provided is a housing comprising the housing part, and an auto-injector comprising the housing.