Extreme Heavy-duty caster blocks are beefed up with extra material for even more strength. Built to take a pounding, these upgraded parts are standard replacements for 9180 and 9181-series 2WD Extreme Heavy-Duty Upgrade Kits. EHD caster blocks are also compatible with non EHD parts as well as Traxxas aluminum accessories. Includes 3x26 mm hinge pins (2) and 3x15 mm screws (2).