These rubber bushings insulate the bars of Musser M645, M646, and M656 Bells from their mounting screws - otherwise you'd have direct metal-on-metal contact and nobody wants that.
These are sold in packs of 10. If you plan on completely replacing all the bushings for a set of M656 Concert Band Bells, you'll need 6 packs (60 bushings total); for complete replacement on M645 and M646 Classic Orchestral Bells you'll need 3 packs (30 bushings total).
