Aero Precision's AR-15 Stripped Receiver Set includes an AR-15 stripped upper Receiver and an AR-15 Gen 2 stripped lower receiver. The upper receiver features M4 feedramps, .250" takedown pin holes. The lower receiver features an upper tension screw, rear takedown pin detent hole threaded for a 4-40 set screw, flared magwell, and is marked "Cal Multi". It works with standard AR-15 components. Both the upper and lower receiver are machined from 7075-T6 forged aluminum. This AR-15 model has a matte black hardcoat anodized finish.