Our patented Metal to Metal Sealing Technology creates a permanent zero leak seal. SmartLock Fittings utilize metal ferrules, instead of o-ring seals, and installed with wrenches. As the outer nuts are tightened with wrenches, internal mechanism applies pressure on the metal ferrule, forcing the ferrules onto the tube and/or valves, and creating a permanent indentation that will hold up to average pressure of 1700 psi.