1:64 Scale Classic Pancake Motor Neodymium Traction Magnet for Track Gripping Performance Slot Cars are 100% Compatible with Tomy and AFX Sets The ThunderJet Ultra-G chassis is Auto World's adaptation of the classic "pancake" design, originally developed by Aurora in the early days of electric slot racing. Auto World expanded the design by adding a Neodymium magnet for better control. Still immensely popular today, entire slot racing events are created around this chassis. ThunderJets Ultra-G are retro slot racing at its best!