Get a grip on your tandem tires with a BAL Wheel Chock. Extend or retract both front and back chocks by turning the large center wing nut for a custom fit between tandem tires. Stabilizes both front and back tandem wheels. Zinc-plated steel resists rust. Diamond tread design provides a sure grip. Adjusts from 15 1/4" to 22 1/2"L. 4"H x 3 1/2"W.