The fastest way to increase the chassis stiffness of any year Miata (1990-2020). This part replaces the factory door bushing (made from rubber) and uses a rigid Ultra High Molecular Weight (UHMW) polyethylene material that has high lubricity. Better than Delrin or generic acetal plastics, UHMW allows the door to slide onto and off of the bushing without binding. This bushing also has a proprietary rubber bumper to capture the door's overstrike when it is slammed. Other designs do not have the all-important "bumper" for the door to hit when it is slammed closed - they allow the door to hit hard plastic. This is not good for the door, the power window system, your door speakers, etc. The novel design from GRE has the bumper feature that gives a "soft close" feature to the door system, and then provides the rigid location of the door's rear edge to make the door a structural member.
Designed by the original Miata engineer, this special design bushing is the only version on the market that provides ALL of the factory part's features. This design is copyrighted with patent pending and is only available from Miata Restoration Parts through an exclusive agreement with the manufacturer, GRE.