On this parts fiche the Collar,ex.pipe is the most specified component.
The most reasonably priced component used on the Ft500 Ascot 1982 (c) Usa Muffler is the Nut,flange,6mm.
A sample from the products for the Muffler include: Joint,ex.pipe, Nut,flange,6mm, Gasket,ex.pipe (nas), Washer 6mm.