Weights are one of the most important factors when building a winning PineCar racer. The heavier your racer is, the faster it will go! Most racing specifications require your racer weigh as close to five ounces as you can get it, but must not exceed five ounces. Combo Weights are easy to install. Drill a 3/8 inch diameter hole in the car and install the weight in the hole. Fill the hole with Body Putty (#3928 Sold Separately), sand when dry, then paint. You can also attach the weight to the side of the car. Cut off the weight you need, keeping car as heavy as specifications allow. Made of a lead-free alloy. Each bar weighs approximately 1/2 ounce.