RifleBlok 556 universally fits into any rifle chambered in .223 Remington/5.56 NATO. Each RifleBlok 556 comes with one (1) RifleBlok, three (3) MagBlok 556 magazine inserts, and an instruction booklet. Your firearm does NOT have to be disassembled to use RifleBlok. Simply insert RifleBlok to train, and remove it to return your firearm to its ready state. RifleBlok is SAFE, REALISTIC, TRAINING!