All Stainless Steel Construction includes a 25rd Magazine. Works in most 5.56/.223 chambered rifles.Just swap this drop in conversion with the bolt carrier group from your 5.56/.223 chambered rifle and you will be ready to shoot .22LR. Ships with 25rd 22LR magazine. For best performance use a round style hammer as notched hammers can cause function issues and 36 grain plated nose bullets have proven to be the best choice for function.