I recently ordered two Leupold zero stop shim kits from the custom shop for $10/ea. Apparently, they only work in M1 style turrets. They arrived with no instructions or illustrations, and my email to Leupold went unanswered. I was also surprised that I could find no internet chatter about this zero stop system either. So I had to experiment. Removing the M1 turret caps from each of my scopes, I was able to stack two of the washer shaped shims of differing thickness within the turret body and replace the turret until finding the right combination of shims that prevented the turret from being dialed very far below zero. One stops half a MOA below zero point, and the other about 2 MOAs below zero. Both work fine for the purpose of reassuring me that I'm not a full revolution above or below my zero point. I am curious what experiences others have had with this zero stop system? Also, my rifle builder cautioned against turning the turret knob hard enough to smack against the point of zero stop for fear that the fine threads on the turret spindle could become stripped. Has anyone ever heard of that actually happening?