This custom machined Delrin part replaces Williams 03-8486. It is a washerlike flange that sits at the bottom of the eyes open coil in Rudy's head, and acts as an alignment flange and coil stop. This part often breaks into pieces. The vertical plunger can then damage the eyelids, its plastic arm, and the coil bracket. Delrin is a very strong plastic that won't age and crack like Nylon.
This part is used on Funhouse and Roadshow.
More information on the head rebuild: http://www.iobium.com/funhouse_plunger_plastics.htm