Soft Tungsten Alloys Tacky Weight

Roll this malleable weight on your leader to match your desired sink rate. Tungsten is heavier than lead and is soft in cold or warm weather.
A fair substitute for the old product was lead and much more pliable. This stuff get's super hard and tough when the weather is cold and very hard to work with. During the hot summer months it is more users friendly. It is like pulling on an inter tube. It does stay on the leader quite well once you have it formed.
You can roll this soft putty–like mixture into your desired shape. Soft and malleable in cold or warm weather heavier than lead. Placing it over a knot like the one you have at the tippet-leader connection to ensure that it doesn't slip on the leader. The material stays soft and malleable in cold or warm weather, and is heavier than lead. Tacky Weight is also great to use on your clinch knot, to create a beachhead fly. And you can use it on your tying thread to form the body on flies for the perfect amount of weight for smaller flies.
Definitely reusable so one pack lasts a long time.

Why Tungsten is better than zinc or lead weights？

Tungsten gives you an advantage because it is about 1.8 times denser than lead, which means tungsten is about half the size for the same weight.
Since pinewood derby cars are so small it is important to place weight exactly where you need it.
The single tungsten cylinder on top (.5oz) weighs nearly the same as the three zinc cylinders (.75oz) on the bottom.
This gives you more flexibility in your car design, because you can place weights more precisely in a smaller area for speed.