This is a CMMG Conv Kit known as the Bravo chambered in 22 LR, model 22BA62F.
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 a 10rd 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.
All Stainless Steel Construction
Includes a 10rd Magazine
Works in most 5.56/.223 chambered rifles.