The component with the lowest price in the REAR ARM schematic is the Washer,spring.
forty-nine components are shown in this Xt350 1986 55v Europe 2655v-300e1 Rear Arm exploded diagram.
A sample from the products for the Rear Arm include: Rear Arm Comp., Oil Seal (2j5), Nut, Self Locking (23x), Washer,spring.