This is a Limbsaver Recoil Pad known as the Grind Away, model 10541.
LimbSaver's Grind-To-Fit Recoil Pads are the go-to pads for gunsmiths and custom gun shops all over the world. Upgrade the value of your firearm with a Limb Saver Grind-to-Fit Recoil Pad. It will reduce up to 70% of felt recoil and dramatically reduce muzzle-jump. That means that you will have greater comfort while shooting and will be able to keep shooting longer without the pain and bruising you're accustomed to. Grind-to-Fit recoil pads offer the greatest customization of any Limb Saver recoil pad. They are designed to be perfectly tailored to fit your stock using a belt grinder. Limb Saver recommends that professional shops modify and install these pads.
Features:
Size Small- 1 LOP 4-13/16 x 1-/27/32
Grindable to 3-7/8 x 1-11/32 for a customized fit on standard stocks