Factory Pro RC XM1 series low-friction belts
Coming from Factory Pro RC and made for the Xpress XM1 and XM1S M-class 4WD touring cars are low-friction drivetrain belts. The white belts are designed to reduce natural drivetrain drag for improved overall efficiency and thus increased acceleration, top speed and run time. The belts are available separately as 144T/432mm front and 57T/171mm rear variant.
Source: Factory Pro RC [facebook.com]