Some items from this specific schematic: Rubber A,stand, Collar,ex.pipe, Gasket,ex Pipe (nas), Muffler Comp,l,ex.
On this parts fiche the Collar,ex.pipe is the most specified component.
The most reasonably priced component used on the Cb250rs 1980 (a) Sweden Exhaust Muffler is the Nut,flange,6mm.
