We recommend PLA for most parts of the model. We have the best experience with Fillamentum PLA or Prusament PLA premium printing materials. Most parts do not matter the filament quality, but some parts may be very sensitive – for example, the gearbox gears, motor pinion, and differential gears. • Tested material for the gearbox gears is PLA, as it is very rigid (PET may be surprisingly fragile!). Just use some high-quality PLA – you can test it by flexing the end of the filament on your spools and you will see which one is fragile. The top option for extra durable gears is the Prusament PC Blend. • For motor pinion, you should use ABS or CPE, as the PLA is can melt due to the heat from the motor shaft and PET is too flexible (pinion will slip from the shaft). • For differential gears please use PLA, as it is rigid enough for this purpose. • We have the best experience with PLA for the cardan joints.