7.7 lb Counter weight has rounded edges, a bronze bushing, and a non-rotating brass plunger to prevent scaring of the counterweight shaft. The brass plunger is spring-loaded so it retracts when you loosen the thumbscrew. This makes it easier to put on and take off of the mount. These weights are designed for the 1.244" dia. Shaft that is typical on the vast majority of G-11 and GM-8 mounts.