Steel Pipe Fittings
Steel fittings such as elbows, tees, caps, and reducers are available in butt-weld, socket-weld, threaded, and flanged designs, commonly specified to ASTM A234/A403 and controlled by ASME B16.9/B16.11 standards.
https://www.octalsteel.com/product/steel-pipe-fittings-accessories/