Master Recoil - The Align Tactical THUMB REST TRIGGER PIN integrates an ergonomic ledge for the support hand's thumb to firmly lock down against, serving as a brake against muzzle flip to provide the fastest follow-up sight picture. Increased surface contact with the pistol reduces support hand slippage while providing an index point for a consistent high thumbs-forward grip. Swaps in seconds to offer maximum control and speed in Glock and select Glock-compatible pistols for a competitive edge. Reflex Sight Clearance Validation - The upward rotation of the Thumb Rest's extended pad requires the (base) of an optic to complement the footprint of the slide (less than 1 inch wide along the bottom 2.75mm of optic's height (see picture below)). Slide will not install if lever is blocked by extended housings or protective fenced-in control buttons. COMPATIBLE: Holosun 507K, Holosun 407K, Holosun SCS Carry, Holosun EPS Carry (at max edge of tolerance 1.05 in), Sig Sauer RomeoZERO ELITE 1x24MM (without metal shroud), Sig Sauer RomeoZERO 1x24MM (without metal shroud), Shield Sights RMSc Reflex Mini Sight Compact, Olight Osight S, Bushnell Compact Reflex Sight RXC-200 / RXU-200, Primary Arms Classic Series 21mm NOT-COMPATIBLE: Sig Sauer Romeo-X (All versions), Romeo-RS Compact, Vortex Defender CCW Micro Red Dot Specifications for Align Tactical SIG Sauer Thumb Rest Takedown Lever: Manufacturer: Align Tactical Color: Black Finish: Oxide Fabric/Material: Hardened Steel Gun Make: SIG Sauer Condition: New Features of Align Tactical SIG Sauer Thumb Rest Takedown Lever Ledged thumb rest provides resistance against muzzle-flip to return sights to target faster Consistent index point for support hand gripping Ergonomic and natural position Package Contents: Align Tactical SIG Sauer Thumb Rest Takedown Lever What firearm models does the manufacturer say Align Tactical SIG Sauer Thumb Rest Takedown Lever is compatible with? The manufacturer suggests that Align Tactical SIG Sauer Thumb Rest Takedown Lever is compatible with SIG Sauer P320, SIG Sauer M18, SIG Sauer M17, SIG Sauer P365