Buttweld pipe fittings include long radius elbows, concentric reducers, eccentric reducers, and Tees, among other things. Stainless steel and carbon steel fittings are frequently butt welded into industrial plumbing systems to form branches, change course, or physically join equipment to the system. The nominal pipe diameters that buttweld fittings are supplied in are accompanied by a pipe schedule. The dimensions and tolerances of buttweld fittings are outlined in the ASTM standard.