54mm 8 Rib Serpentine Steel Pulley

Most of the time a pulley is just a pulley. But, this is an exceptional pulley:
My MK4 VW 2.0 jetta alternator had a 54mm 6 rib w/extended shoulder on the factory unit.
That pulley diameter cannot be decreased, or the belt will slip.
That serpentine belt is not made in a smaller size.
The extended shoulder on the factory unit, throws off the serpentine parallel alignment (with a larger alternator), causing a few issues.
This pulley turned my paperweight (not mechman) into a functional HO alt.