This component was designed as one-half of the very-high-ratio belt drive system in a hobby wind turbine. The turbine turned out to be a bit of a dud due to issues with the dynamo*, but the pully works perfectly. It's got a decent flange for keeping the belt in place (I had so many issues with belts slipping off while I worked out the best way). The upper flange is a 'crenulated' design - they all smudge together when printed, but it makes the overhang a lot easier to print. That's my own innovation - I don't think anyone else has thought of that trick.
One piece of advice though: Rubber bands do not last. They degrade over time. Get a proper drive belt if you don't want to be replacing it every month.
*The textbooks lie: You can use a DC motor as a dynamo, but they suck.