There are two designs of compressor wheels used in TD04/TE04H & TD05/TD05H/TD06 turbos: flatback and superback. The flatback compressor wheel is totally flat in the center, it is not beveled or indented. The superback wheel is beveled or tapered. The difference in the kit components is with the thrust collar and the seal plate. The thrust collar for the flatback wheel is taller than the superback thrust collar. The seal plate for the flatback wheel is flat whereas the superback seal plate is indented. Listed below are compressor wheel models that use each design.