Clamp-on steel extension adds a serrated lever to the side of the hammer spur to give your thumb a large, easy-to-find horizontal grasping surface. A must-have if using a low-mounted scope, heavy gloves, or you just want a hammer that's easy to grasp under stress or in wet weather. Hollow design keeps weight to a minimum, so hammer speed and locktime are unaffected. Holds tight on left or right side of hammer with steel Allen head screw. Mfg: Grovtec Us, Inc. SPECS: Steel, blued, matte finish. Extension - 5⁄8" (15.5mm) long x 3⁄8" (9.2mm) diameter. *Including Big Bore and angle-eject (not 94/22). ** Including 39A, 39M, 1894, 1894C, 1895S, 336C, 336T, 375, 444S, Glenfield 30A.