RC500 features a standard trail compound and 10-ply carcass which utilizes a reinforced lower sidewall and heavier ply cord resulting in extreme durability.? The new carcass maximizes ride quality and the track ability is unmatched on loose or hard pack terrains. RC500S, the ?S? or ?sticky compound? features a combination of our proprietary soft tread compound and flexible 8-ply rated carcass which results in one of the best rock crawling Tire on the market. The soft compound and carcass flotation set a new standard in slick surface traction.