Also widely produced are semi-automatic and typically longer-barreled derivatives of select-fire submachine guns, such as the FN PS90, HK USC, KRISS Vector, Thompson carbine, CZ Scorpion S1 Carbine and the Uzi carbine. In order to be sold legally in many countries, the barrel must meet a minimum length (16" in the USA). So the original submachine gun in given a legal-length barrel and made into a semi-automatic, transforming it into a carbine. Though less common, pistol-caliber conversions of centerfire rifles like the AR-15 are commercially available.