Whether you want the smoothest shooting carbine possible or are looking for added reliability while shooting hotter loads or suppressors CMMG’s Action Tuning Kit* gives you the added flexibility to make the MkG45 GUARD perform exactly how you like it. The optional Action Tuning Kit allows you to adjust the action to your preference much like changing buffers or changing gas port settings on an adjustable gas block. – Included: – 1oz weight – 2oz weight – 3.4oz weight (standard 9mm) – (3) .250 x .625 roll pins