To maximize performance, Pinewood Derby cars should be weighted to the maximum weight allowed. PineCar #P354 Combo Weights are easy to use - just drill a 3/8" hole in your car and insert weights or attach to the side of your racer. They can be cut with a razor saw or hacksaw to fine tune your car's weight. Package contains 4 weights of approximately .5 ounce (14.1 grams) each. Choking hazard - not for children 3 or younger.