ICON 17in Compression/Alpha/Rebound Wheel Rock Ring Kit (20 Bolt)Constructed from high density polyethylene (HDPE) with UV 770 Protectant, IMPACT Rock Rings protect the outer surface of the wheels from scuffs, scratches, and trail damage. When the terrain gets technical, the tough HDPE ring allows the rim surface to do its job by absorbing impacts and sliding against rocks with less bind, improving performance in the stickiest of situations. The IMPACT Rock Ring Kit includes all of the necessary hardware, providing