Flange gaskets are typically used on pipe sealing flanges from pipe to pipe or pipe to condenser, heat exchanger or evaporator head. Depending on the working pressure of the fluids in the pipe, the flange can either be just a garlock type ring gasket or a full face flange with stamped bolt holes in it. As an example, a 150 lb. Flange gasket is usually just a ring that is 1” wide and 1/8 thick. A 300 lb. Gasket is usually the full face width of the flange with bolt holes stamped in it. It is always at least 1/8” thick or heavier. Many of them are also steel ring reinforced.