- Plain Flat Metal Gasket- Flat metal gaskets are best suited for applications such as valve bonnets, ammonia fittings, heat exchangers, hydraulic presses, tongue-and-groove joints. Flat metal gaskets are relatively inexpensive to produce and can be made of virtually any material that is available in sheet form.- Solid Metal Shim / Washer / Gasket- Pioneer Brand Shims & Washers are manufactured from stainless steel, brass, copper, aluminum & phosphor bronze in Round, Square, Rectangular, Oval & Hex shape.- RTJ Joint Gasket- Ring type joint gaskets come in two basic types, an oval cross section and an octagonal cross section. These basic shapes are used in pressures up to 10, 000 psi. The octagonal cross section has a higher sealing efficiency than the oval and would be the preferred gasket. Dimensions for API ring joint gaskets and grooves are covered by ANSI B16.20 and API 6A.