Midwest Industries Lower Receiver Block, Polymer Construction, Fits 223 Remington/556NATO Receivers, Blue MI-LRB Midwest Industries is known for bringing the highest quality manufacturing processes and accessories to the firearms community. With their long history" they are pleased to bring their tricks and knowhow of building quality firearms to the end user's workbench with their high strength polymer Mag Block. Utilizing either the .223 Remington/5.56 NATO or the .308 Winchester/7.62 NATO AR receiver sets" this new mag block makes some of the most tedious tasks in building an AR-style firearm fast and simple. With features including a gas block roll pin installation section" a trigger guard installation section" a fire control pin assembly" and many other applications outside of its classic use" this lower receiver block will be the key to building your next firearm. Made in the U.S.A.