They absolutely do not work. They were first generation "vibration reduction" so to speak. Been outabout sevenor eightyears. I ordered them out of a Cabelas archery catalog.We crono'd my old High Country Four Runner way back when they came out. It was always slower no matter where we put them. They claim there is a sweet spot, but I wore out the those little screws looking for it.Irhuntr is right, nothing put on makes a string faster.