Sylvan Arms SCB100: This fantastic conversion kit from Sylvan Arms is one of the best accessories on the market today and increases the modularity of your AR-15 pattern rifle. This 9mm Sig P320 Magazine Conversion Block converts your standard AR-15 lower receiver magazine well to a 9mm Lower using P320 9mm magazines. The fit and function of this adaptor are exceptional. All Sylvan Arms products feature a limited lifetime warranty and are proudly designed, built, and assembled in the USA!This Sig P320 9mm Conversion Block is genuinely ingenious and one of the best AR-15 accessories on the market today. This 9mm Sig P320 Magazine Conversion Block converts your standard AR-15 lower receiver magazine well to a 9mm Lower, allowing you to use P320 magazines. This conversion kit is designed to fit into the magazine well of your standard AR-15 and reduces all the extra space and allows for use of Sig P320 15rd, 17rd, and 30rd magazines. This is fantastic because it increases the modularity of your standard AR-15 pattern rifle by enabling you to change from 5.56 to 9mm by utilizing this adaptor and merely changing your upper receiver and BCG. This also allows you to purchase standard Mil-Spec lower receivers to build a complete 9mm firearm. This conversion kit is constructed of 6061 aircraft-grade aluminum.