Full Face gaskets are a flat sealing element, consisting of an inner and outer diameter, and a specified number of bolt holes, the center of which are evenly spaced around a bolt circle. Full face gaskets are designed to fill the entire space between flat-faced flanges, with bolt holes that match the size and arrangement of the bolt holes in the intended flanges. ASME B16.21 and ASME B16.47 govern the dimensions of full face gaskets for standard and large diameter pipe flanges. EPDM, Ethylene Propylene Diene Monomer, is an "M" class synthetic rubber elastomer. Relatively immune to sunlight, water and low temperatures, EPDM is often a smart choice for gaskets that will be outside. Good compression set resistance means it recovers well in applications where a joint may open up from time to time, and high electrical resistance means EPDM gaskets may be appropriate for some electrical installations.