Socket weld flanges are similar to slip on flanges where the pipes are connected by inserting the pipe into the socket of the flange except that the flange has two dimensions: bore and counterbore. The counter bore is slightly larger than the outer diameter of the pipe whereas the bore has similar diameter as the inner diameter of the pipe. A stopper is placed at the bottom of the bore for the pipe to rest on. Unlike slip on flange where the fillet weld is applied on outside and inside, socket weld flanges are fillet welded on the outside only. It is available with flat face, RTJ face or raised face. They are mainly designed for smaller sized pipes.