"Replaceable polymer inserts last for 500-700 mounts/dismounts and change in seconds. Eliminates hassling with booties that slip off the combo tool. Not for use with steel wheels. U.S.A. Accessory Type Mag wheel inserts, Material Polymer, Recommended Use Tire change accessory, Dimensions L x W x H in. 7 x 3 x 1. Not for use with steel wheels"