Hi Vis Wreckmaster Slippery Jims set of 4. The skates dramatically reduce friction during the loading and unloading of vehicles with damaged or stuck wheels. The skates wedge between the wheels and the ground, minimizing friction, meaning less stress on your winch and wire rope. With skates in place, the disabled vehicle will slide easily into the loaded or unloaded position. The skates have an interlocking tooth system. The skates can be joined together to form larger skates for wide tires. Each skate also has a notch to accommodate vehicles without wheels. Slippery Jim wheel skates are constructed of a super tough polymer for greater durability.