I really like the look of it and can certainly appreciate the engineering that went into it. I'm actually doing one of those "why didn't *I* think of this" things. The real question revolves around materials and build quality. They've built this within the very limited confines of the stock pulley thickness plus the 1/4" or so of the old spacer. I'm here to say this: Holy Crap, there isn't much room there to create three layers of independently movable components plus the needed bearings and retain something close to the expected strength and durability. I'm going to assume that it's necessarily made of *steel* for sufficient strength of these thin pieces. So, I would also assume that the negatives on this would appear to be 1. cost 2. weight. 3. durability but damn, it looks like a great idea if #3 proves sufficient.