Magloc Duty M 4S for Glock Gen 4 and 5 Small Grip (Standard Grip) Recoil Control Thumb Rest 1785 US Patent D472,599. Reduces muzzle jump by 70% (shooting weak hand only) Beaver tail length: Competition - 9mm (0.35") ; Duty - 2.7mm (0.11") Wings can be modified with a file to fit different hand size. Avoids slide cut on web of shooting hand, increase shooting speed and accuracy No modification of your firearm is required. Fits Gen 4 and 5 small Grip Glocks.