Barrel Blok brand muzzle block and visual safety indicator. BarrelBlok was designed for use in semi-automatic pistols so the user could realistically train while maintaining the full mechanical functionality of the firearm. Each BarrelBlok comes with one (1) BarrelBlok, three (3) MagBlok magazine inserts and an instruction booklet. Your firearm does NOT have to be disassembled to use BarrelBlok. Simply insert BarrelBlok to train, and remove it to return your firearm to its ready state.