The 440-X2 pick-up shoe springs produced by Tyco work just as well on Mattel chassis. They are used to keep tension on the pick-up shoes in order for them to stay on the rails. This results in more power being transferred to the chassis. You'll want to keep spares of these since their size makes them difficult to find if dropped. We will only sell them in sets of 2 pair only. Buy in quantity and save!!!