In a fluid pressure regulator, the combination comprising a body forming a cavity and a cap on the body extending over the cavity, the cap and body carrying interengaging threads allowing rotary make-up of the cap on the body; a diaphragm in the cavity and seated on a ledge formed by the body, thereby to form a seal; a pressure transmitting element in the cavity to transmit cap pressure to said seal, the body having flow porting and there being a poppet in the body and movable to control fluid flow via the porting; a spring in the cap and structure in the cavity and axially movable to transmit spring pressure to the diaphragm, the poppet carried for axial movement with the structure, and blocking means to block relative rotary movement between the pressure transmitting element and at least one of the body and the structure.