Carbon Steel Ring Type Joint (RTJ) forged flanges have grooves cut into their faces which accept steel Ring Gaskets. Carbon steel RTJ flanges seal when tightened bolts compress the gasket between the Carbon steel flanges into the grooves, creating a metal to metal seal, deforming the gasket to make Intimate Contact inside the grooves. Carbon Steel A105 Ring Type Joint Flange Size Range : ½” NB to Up to 60” NB Subject to Type of RTJ Flange.