Minimum caliber is 9mm.  Pistols are limited to 6 rounds.  Electronic/optical sites are not permitted.  Barrels may not be compensated or ported.  Race-type holsters are permitted and there are no restrictions on the position of the holsters and speed-loaders.  The most common calibers used are .38, .357 and .45, with pistols modified to accept "moon-clips."  Cosmetic modifications that do not give a competitive advantage are allowed.  Smith and Wesson are the most common pistols used.