A sprinkler assembly (10) having a receiving member (12), a fluid tight seal (44) and a sprinkler frame (14). The receiving member includes an inner surface (22) defining an internal passageway and a central axis (A-A) of the assembly. The frame of the sprinkler includes an internal surface (38) that defines a fluid passage. The sprinkler assembly includes cooperating positioning elements (28, 40) which engage and couple the sprinkler frame to the receiving member for at least one of an axial and rotational adjustment between the frame and receiving member. The engaged positioning elements facilitate formation or location of the fluid tight seal between the sprinkler frame and receiving member, the seal being spaced from the engaged positioning elements. In one aspect of the assembly, the sprinkler frame and receiving member are made of plastic material (e.g. CPVC).