Compression fittings (sometimes named "lock-bush fittings") include a tapered, concave conical seat; a hollow, barrel-shaped compression ring (at times named a ferrule); and also a compression nut which is threaded onto the body in the fitting and tightened to generate a leakproof relationship. They are generally product of brass or http://deankargv.blogproducer.com/45499/5-simple-statements-about-valves-and-fittings-explained