These pucks attach the Old Man Mountain rack frame to the front or rear of your bike. They provide a secure upper attachment point for the rack. Included in the packet are heavy duty zip ties, clear protective film, and mounting hardware. Designed for use with carbon, steel, titanium and aluminum bikes and forks. Slots in the puck also allow for use with metal hose clamps (not intended for carbon). Pucks can be left on the bike for future reinstallation of the rack.