Absolutely essential item for 4-wheel escape on everything from solid ice to sand ( not over 6 ft. deep mud holes) is 100% wool, made in the U.S.A., and stamped accordingly U S Army blanket. It has worked 100% of the time for 45+ years-same blanket-even on solid ice, 8 feet at a time. There is one in the trunk of every car in my family. Guaranteed to keep one wheel ( at least) at a time from spinning.