This Counterweight Mounted Carbon Fiber for RC4WD, there have 3 kits:
Kit A : Only Carbon fiber and screw, you can DIY counterweight by yourself.
Kit B: RW02 it has included 4pcs tungsten steel(Appr 32g/pcs), it can direct use RC4WD axles.
Kit C: RW03 it has included 6pcs tungsten steel (Appr 32g/pcs) and 2pcs 7075 aluminum alloy 15mm Hex Hub.