As you can see in the pic, the outer (smaller) pulley looks to be the same size as the stock one. However, the inner (larger) pulley appears to be a bit smaller than stock. I thought this thing was the same size as the stock pulley (no underdriving)? The instructions say to use only one stock size belt...the other size is different (larger I would assume).

Anyway, I thought this pulley was the same size as stock (only lighter) but it doesn't appear so. What gives?