Professional Two Stage VTS 250, Oxygen, 540, 9/16-18 UNF (M), 40 PSIGDelrin insert bushing for durability, easier adjusting.Die-forged brass spring housing cap provides greater strength and durability.Stainless steel diaphragm gives accurate long lasting service.Stem-type seat mechanism inlet pressure aids in sealing.Stainless ball in key for easy adjustment.