The Brownells AR-15/M16 Receiver Taps & Dies are made from a high-speed steel that easily chase and clean up the two most important threads on the AR-15/M16 receivers. The 1-1/4"-18 TPI corrects out of spec or cross-threaded upper receivers and barrel nuts. The 1-3/16"-16 TPI makes the receiver extension tube and lower receiver threads uniform for easier installation.