A coupling pin for use in a pump housing, the pump housing including an outer casing and an inner pump liner, the coupling pin being suitable for locating the liner and casing relative to one another, the coupling pin including a shank and a head at one end of the shank. The head includes a cammed surface thereon which is adapted to co-operate with a follower on the liner, and a locating section on a remote or terminal end of the head which is adapted to be positioned against a seat in the outer casing when fitted. The arrangement is such that rotation of the coupling pin causes the follower to track along the cammed surface so as to cause relative movement between the outer casing and the inner pump liner.