The Uzi uses an open-bolt, blowback-operated design, quite similar to the Jaroslav Holeček-designed Czech ZK 476 (prototype only)[19] and the production Sa 23, Sa 24, Sa 25, and Sa 26 series of submachine guns. The open bolt design exposes the breech end of the barrel, and improves cooling during periods of continuous fire. However, it means that since the bolt is held to the rear when cocked, the receiver is more susceptible to contamination from sand and dirt. It uses a telescoping bolt design