Finally go inverted without weeble wobble!!! This upgrade replaces the stock o-rings...however, they are double the width of the Esky ones so need to be cut in half for use with the Belt CP. The advantages of these dampeners is simple. They are able to produce a more responsive and tighter head dampening response by filling the entire dampening area of the head block with material. The dampeners are designed specifically for the T-Rex 450XL/SE head block and spindle, giving a tight dampening solution without needing to over-compress the rubber with spacers. Also, because of their shape and material, the Pro T-Rex Head Dampeners are able to last much longer.