"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, Dimensions L x W x H in. 7 x 3 x 1, Material Polymer, Recommended Use Tire change accessory. Not for use with steel wheels"