Abstract: An adjustable drop or riser nipple for sprinkler systems and the like, characterized by few, simple parts and comprising short, telescoping inner and outer lengths of pipe having interposed between them a locking or drive ring which acts against an expansible, resilient sealing ring so as to lock the pipes in any of different adjusted axial positions as well as to seal the same to each other. The locking ring is part of an exposed nut threaded into the projecting end of the outer pipe. The outer pipe intermediate its ends has fixedly attached in it an abutment ring which engages one end of the resilient sealing ring in the pipe.