All-Terrain Formula (ATF) wheels are poured in a special soft urethane we call All-Terrain Formula or (ATF). ATF wheels are excellent for rougher terrain so regardless of road quality, this revolutionary formula will roll you there quickly and smoothly. Rough Riders feature the H5 Hub. H5 Hub Benefits: Chemically bonded for an extremely strong hold. Smaller hub radius for smoother ride. Widened core to support complete wheel. Maximizes roll for more speed over rough terrain. Take the road less traveled. These measure 56mm x 40mm with an 80A hardness.