These brass fittings are traditionally used for connecting steel pipe with threaded ends.  Size designation is related with the internal diameter of the pipe. Typical applications include water supply and distribution systems, for both cold and hot sanitary water, in heating, cooling and air conditioning systems as well as irrigation, sprinkler fire piping or other piping systems with pipe threaded ends.
VMS stocks threaded brass fittings in sizes ranging from 1/8” through 2” and in all available shapes including unions, changes of direction (bends, elbows), branches (tees), bushings, extensions, plugs, nuts, reducers, couplings etc., allowing for unlimited possibilities of connection.