Combo Weights are easy to install. Drill a 3/8" diameter hole in the car. Place the flat side of two weights together to make round weight and install the weight in the hole. Fill hole with body putty, sand when dry, then paint. You can also attach weight(s) to the side of car. Cut off the weight you need, keeping car as heavy as race rules allow. Made of a lead-free alloy. Approx. 0.5 oz. (14.1 g) each.