The socket welding flange is similar to a slip-on flange except it has a bore and a counterbore dimension. The counterbore is slightly larger than the O.D. of the matching pipe, allow in the pipe to be inserted into the flange slimilar to a slip-on flange. The diameter of the smaller bore is the same as the I.D. of the matching pipe. A restriction is bult into the bottom of the bore which sets as a shouder for the pipe to rest on. This eliminates any restriction in flow when using a socket welding...