Pro Axle Guide is a precision machined aluminum block with a laser cut tab designed to fit in the axle slot of most P.W.D. race car bodies. The tab is designed to precisely space the wheels from the body. The block can also be used on the flat side for extended wheel base cars. The Pro-Axle Guide will improve the speed of your pinewood derby car by ensuring accurate mounting of axles: 1. Axle Insertion - Ensures accurate mounting of axles (in axle slots) to improve alignment. Accurate alignment is critical for top speed! 2.Wheel-to-body Spacing - Establishes the correct gap between the wheel hub and car body. The proper gap minimizes car wander and reduces excess contact between the car body and the wheel hubs. 3.Reduced Risk of Block Damage - During the insertion process the Pro-Axle Guide provides support to the wood around the axle slot, minimizing the risk of damage.