This is a spare pulley plastic part for the TRF420 racing chassis machine. Use it to replace worn out pulleys in your drivetrain to keep your car running efficiently and smooth. - TRF420 37T Differential Pulley x1 - TRF420 Differential Case x1 - 0.2mm & 0.3mm Shims x2 each - The new design not only provides a weight savings of 1.5g, but also provides less oil leakage compared to previous designs. - Compatible with TRF420 and TA07 chassis cars.