Parts such as the Rear Arm: Nut 240221430000, Brg,cyl-cal Roller 14.5g Tm, Oil Seal (20.9x28x4-1w1), Bearing, Thrust are included in the Tz125 1980 (a) Usa Rear Arm parts fiche.
The Rear Arm is made up of components including this Bearing, Thrust which is the most expensive.