NOTE: THIS FITS THE TA51 MOUNT. PLEASE INFORM US IF YOU HAVE A QUICK DETACH MOUNT. WE WILL SEND THE CORRECT ONE. NOTE: THIS DOES NOT FIT ACOG CLONES. IF YOU HAVE A CLONE NOTIFY US AND WE CAN MAKE ADJUSTMENTS TO FIT. The REM ACOG illuminates the reticle of the Trijicon ACOG TA31 / M150 sight in low light conditions and reduces the reticle bloom in bright daylight. It eliminates the need for ChemLight sticks and it eliminates the need to replace the Tritium. It has 11 brightness settings so the user can adjust it to their desired brightness. The REM ACOG is designed so the Trijicon TA91 Tennebrex Killflash Anti-Reflection Device can still be used. Reticle Bloom: The REM ACOG is designed to cover half of the fiber optic of the sight to reduce the reticle bloom that happens when out in bright daylight. Durability: It is Made of a 30% glass filled Polymer just like the pistol grip and hand guards. Water proof and dust proof. Tested at 0 degrees F to 120 degrees F. Watch this review in this video. Start time at 8:34 and ends at 13:25 https://www.youtube.com/watch?v=1CCGjZ4pzCU