"When loading docks are uneven, gravity works against your team when unloading and loading cargo. Instead, eliminate the safety hazard by implementing HD Ramps Adjustable Trailer Wheel Risers. The adjustable height design allows you to set the height from 5"" to 12"" in order to properly level off a trailer when backing it up to a loading dock. Manufactured from high-strength, lightweight aluminum, these 66"" L wheel risers work with single axles, and are wide enough to accommodate 18"" W single wheels. Sold in pairs, this set of two risers supports up to 40,000 lbs. and has serrated rungs built into the surface for maximum traction in inclement weather as well as icy conditions. Four stainless steel handles per riser provide hand grips for manually repositioning."