Made of high quality brass pipe couplers. High hardness, high strength and superior anit-corrosive. 6 locking steel balls for increased life and holding power. Prevents leakage from water, oil, air, steam and fluids under pressure. Great for also blocking off intake manifolds water, pumps, ports. The role 1/4in. NPT pipe fitting coupler is sealing. Designed to create a tighter seal. Temperatures range from -65 to 250 F. Includes 10 pieces of brass male couplers. Maximum air pressure 300 PSI.