Pinewood Pro Derby Car Weights - Tungsten Putty Fine Tune Car Weight for Fastest Speed (1 Ounce) QUALITY - Tungsten Putty is a non-hardening, moldable material made from tungsten powder and a polymer binder. TIME SAVER - Easy for fine-tuning pinewood derby car weight and for making fishing weights FLEXIBLE - Tungsten putty weights are easily shaped and placed anywhere on your pinewood derby car. UNIVERSAL - Use as weight for derby cars or for fishing weights. DENSE - Small but heavy means you can add weight to your derby car exactly where you need it to optimize center of gravity.