Baja 5B/Rear/Heavy Duty compound is stronger and more durable.

# 4835 - DIRT BUSTER BLOCK TIRE HD COMPOUND (170x80mm/2pcs) Pick up a pair of Dirt Buster Block rear tires in HD  for heavy duty performance for the Baja 5B! The HD compound is a newly formulated blend that resists rips and tears, developed for extreme driving conditions. For optimum performance we recommend using #4812 Molded Inner Foams with these tires (not included).