This is a set of Schumacher 1/10 Short Course Open Cell Foam Tire Inserts. Choosing the right insert for the right condition can be the difference between winning, losing, or just plain having bragging rights over a competitor on the track. Features: Hard density material and construction Extremely light-weight Versatile size, shape fits vast majority of tires Precise contoured manufacturing Durable material, can be re-used Dark Grey color for easy identification Includes: (2) Foam inserts

These are classed as hard compound foam.