The CZ 805 BREN is a gas-operated modular assault rifle designed and manufactured by Česká zbrojovka Uherský Brod. The modular design enables users to change the calibre of the weapon to 5.56×45mm NATO or 7.62×39mm intermediate cartridges by quick change of barrel with gas tubes, breech block, magazine bay and magazine. The CZ 805 BREN was created to replace the Sa vz. 58 in the Czech Army in 2006, which later sprung a family of rifles; CZ 807, CZ BREN 2, CZ BREN 2 BR and CZ BREN 2 PPS.