Contacted HKS regarding the part numbers: 1401-RA112 GT3037 52T .73 A/R 1401-RA122 GT3037S 52T .73 A/R Thanks for pointing out that it comes in that trim without the "S" housing. Hopefully I'll save a few hundred dollars when I order the RA112 instead of the RA122 I had gotten a price on. -Brian