BORON ALLOY 10B21 STEEL LASTS UP TO 83% LONGER THAN STANDARD ROCKWELL 53 STEEL. LONG LIFE AND STRENGTH WITHOUT BEING TO THICK. 7.14mm thick. Recommended for over the road, chain law, semi trucks.For plowing or extended use, the Heavy duty truck tire chains below are recommended when available in your size. For easier installation of twisted linkTruck Tire Chains see our Sno-Chain Ramps. Optional rubber or spring tensioners are recommended.