Ball bearings are number 1 list of the M05 chassis upgrade because ball bearings can increase speed and running time compared to stock plastic and metal bushings. Yeah Racing has produced high quality ball bearing set for M05 chassis, yet cheaper price compared to TAMIYA M05 bearing set. I suggest you buy this bearings set along with your new M05 chassis kit. Therefore you can use this bearings to replace the boxed plastic/metal bushing during the initial kit assembly. A recommended upgrades.