The Mil-Spec 7075-T6 aircraft aluminum Anti-tilt Buffer Tube uses carrier cradle extensions to ensure that the carrier is always supported by the buffer tube, even when the bolt is forward. This prevents carrier-tilt and premature wear on the buffer tube. Thusly, the buffer-detent button doubles as a lock that stops the buffer tube from rotating and becoming loose under extreme operation conditions. Our Mil-Spec 7075-T6 aircraft aluminum Anti-tilt Buffer Tube uses "carrier cradle" extensions to ensure that the carrier is always supported by the buffer tube, even when the bolt is forward. This prevents carrier-tilt and premature wear on the buffer tube. Thusly, the buffer-detent button doubles as a lock that stops the buffer tube from rotating and becoming loose under extreme operation conditions. POF-USA's designing also features three extra drain holes for marine environments. Replacement Compatible with All P415 and P416 rifles with 6 position buffer tube. Replacement Compatible with P308 rifles manufactured BEFORE October 2012 that used a 6-position buffer tube. New P308 rifles feature a 7-position Buffer Tube that utilize the standard AR-15 Carbine Buffer and .308 A2 Rifle Length spring. Refer to the first two digits of your weapon's serial number for the year.