Heavy Duty 3/8” thick case-hardened steel. For tractors, backhoes, graders, loaders, scrapers and plows. Case hardened in accordance with ASTM E18 Standards. Snow Chains spacing is defined as the number of side chain links skipped between cross chains. 2 link provides a more consistent ride by having more chain on the face of the tire. 2 links helping to reduce the vibration (bumpy ride) from being on chain - off chain.