100% Satisfaction with LIFE TIME WARRANTY. No Questions Asked. One word - QUALITY Tested with Several car constructions and Painstakingly engineered to Fine tune the Tungsten % in these weights. QUALITY is our RELIGION. CUSTOMER Service is our PASSION. FIRST TO FINISH LINE - EVERYTIME Tungsten weights are place toward the rear of Pindewood Derby car. Greatest potential energy is generated as a result of higher center of mass on the track resulting in maximized kinetic energy = Always First to the FINISH LINE :) SAFE - CHAMFERED edges Being non-toxic makes our weights safe to handle as opposed to lead. No Sharp edges and Easy to handle EASY INSTALL Cylinders are 3/8? diameter (standard drill bit size) With chamfered edges, these cylinders will slide easily into your drill holes VERSATALITY EASILY TUNE FOR MAX SPEED - Multiple sizes make Easiest and Precise fine tuning of your Pinewood Derby car. INSTRUCTIONS Drill a 3/8 inch hole using a standard electric drill. Insert weights. RACE. For Tech Buffs - SMALL & DENSE Tungsten is 1.7x denser and smaller than lead. It is 2.7 denser than zinc making it about 1/3 the size of zinc! The following % are fine tuned to generate maximum inertia producing MAX speed at the finish line Class 3 tungsten, 95% pure. It is an alloy of 97% pure tungsten, 3% nickel and iron WHATS INSIDE Package contains eight 3/8" diameter cylinders with chamfored edges for easy insertion. The four .5oz cylinders are .44" long, two .3oz cylinders are .27" long and two .2oz cylinders are .18" long. With this package of incremental weights you will be on your way to a fast pinewood derby car.