Top surface. Despite all the CNC and material trickery Alutec can't center the wording properly on the crank pulley. Bummer! The Alutec crank pulley is the same diameter as stock crank pulley so no underdriving s**t! If you're running any semblance of a half decent ICE system stay far far away from underdrive crank pulleys. Alutec uses 7075 aluminium alloy material which is stronger than 6061 alloy used by the likes of Unorthodox Racing and majority of performance pulley manufacturers. Even the adjustable cam pulleys on the SP were 6061 material only. This along with the hard anodizing will greatly reduce wear on the pulley's surface in the long run.
Like the stock crank pulley the Alutec version has nicely machined grooves for the stock belting.
Bro Uncle Fooyc got so excited he promptly got himself one. SMS from him late last night "Cb! Dem nice. I'm going to hug it to sleep!" Wahahahaha! Acceleration in the lower gears should improve with the crank pulley fitted. Hopefully max power output too! Uncle Foo will be installing first and also doing a dyno. I'll install when I can find some time off work and renovating my house. Stay tuned for a follow up.