High Quality Seeburg motor couplers. Made with all new material heat vulcanized in original Seeburg molds. There were a few different revisions over the years, and this design with the flutes on the side are deemed the best design by Seeburg. Your old dried out / hardened coupler could be causing vibration through the mechanism and be heard in the playback, also if dried off center you can experience motor fatigue while it has to spin an off center, non-flexible coupler. In some cases, the couplers break and separate completely.
Motor coupler for main mech drive motor for all Seeburg Models M100B and newer.

Part Number 49-1947