Different from tees, crosses are four outlets. According to difference of outside diameter for each outlet, there are Butt Weld Equal Cross and Butt Weld Reducing Cross. For equal cross, the size for connecting run pipes are same. But for reducing cross, the size for connecting branch pipe is smaller than run pipe`s.
The materials of pipe cross are carbon steel, alloy steel and stainless steel. Manufacture standards are ASME, GB, JIS, DIN, GOST etc. Similar to other Pipe Fittings, there are Seamless Pipe cross and weld pipe cross. They shall be directly welded with Steel Pipes and have many applications, like petroleum, chemical, shipbuilding, construction etc.