Just Miata JMWGB01 - Window Guide Bushing (Set of 2) The Window Rear Guide Bushing also stabilizes the rear portion of the window and keeps the window from rattling around at the rear. Comes in Set of 2. One bushing is needed per window or per side of car. This Replacement Window Guide Bushing is made out of Delrin, a self-lubricating plastic that should last the life of your Miata. Without the Window Guide Bushing, the window glass will shift and bind at the front edge of the glass inside the weather strip and slow window operation down as the window travels up and down. You can't buy this bushing from the dealership separately, you have to buy the entire window. Ouch!