WP DD Washers Belts?
There is actually a foam rubber belt around the outside of the brake drum, its only purpose is to reduce the ringing sound when the brake is disengaged as the washer goes into spin.
Sometimes when a drive cupping breaks and a customer moves the washer from its installed position they find this thin rubber strip laying under the washer and they bring it into the parts store and try to buy a new one thinking this is why the washer is not working, LOL.
The drive cupping with the metal insert is the best one that WP has used yet in their DD washers and is the one they are using in the new DD washers that are currently in production, I recommend it.