I shot one all last year and my equipment was checked by IBO officals. These things are allowed by the rule book. I cant quote the page its on but I have seen it in their. It makes a special reference to a dampining or vibration reduction device. Or maybe Iam just thinking I read it in their. But I do know that if you put one on the front of your stablizer it counts as the total length of your stablizer. Look real hard at the rules its in their somewhere. My equipment was checked very closely at Erie and the enhancer on the back of my riser was never mentioned. If you think those things make you shoot better then they do.