This is a optional Tamiya Lightweight Front/Rear Universal Shaft Set, and is intended for use with the Tamiya TRF801Xt. The lightweight of these Universal Shafts is achieved by reducing the shaft diameter from 4.2mm to 3.4mm. The weight of a single standard shaft is 35g, compared to the lightweight shaft which is 29.5g, which equals a weight saving of 5.5g. Which means when all four shafts are replaced, you can save a total of 22g of rotating mass.
Eliminating weight from the drive train of your vehicle is often the first upgrade recommended by pro racers, regardless of the brand of car you drive. Reduced rotating mass will aid in smoother acceleration, faster spool up, shorter braking distances, and will help you achieve faster lap times on the track.