Molded from tough fiber-reinforced rubber compounding! Just a smart thing to do to keep you safe. One year warranty, 8" x 5.75" x 9", 9 lb weight. ANSI® Z133-2012 5.1.12 When units are left unattended, keys shall be removed from the ignition, the wheels chocked, and, if applicable, the parking brake applied. 5.1.17 Towed units that are detached from another unit (for example, a motorized vehicle) shall be chocked or otherwise secured in place. 5.2.4 Wheel chocks shall be set before using an aerial device unless the device has no wheels on the ground or is designed for use without chocks. Sold in a box of 2 wheel chocks.