BarrelBlok™ 357 universally fits into any semi-automatic pistol chambered in .357 Sig. Each BarrelBlok™ 357 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. BarrelBlok™ is SAFE, REALISTIC, TRAINING!