This TAMIYA (#50477) 24T, 25T AV Pinion Gear Set can only occupy both 55T and 58T spur gear of the TAMIYA (#53665). I test run my TT-01 gear ratio setting (5.72:1) by installing the 58T pairing with 25T pinion gear on TAMIYA Sport Tuned Motor. Note that I am using TAMIYA semi slick tires set and full ball bearings on my TT-01. After the test run I have notice sacrificed acceleration but have high top end speed. My TT-01 runs very fast compared to stock gearing. The TT-01 sounds much quieter due to heavy motor loading and I can hear my TT-01 'cutting the wind' as it passes by me. The sound I described is very cool. I recommended this upgrade for long car park bashing or racing at large circuit.