We sell quite a few here and they are an extremely well made product. The result is always the same for people, a noticable difference in acceleration due to the large of amount weight savings and less inertia required to turn a lighter component. The underdriven kit comes with a proportional change in size to the alternator pulley diameter so that alternator speed remains the same. MSRP is $195 for the 2 piece and they come in Black, Silver, Red, Blue, and Purple. Hope this answers your question.
Troy Fankell
Fltirons Subaru