Just a style thing. Yells doesn't fit. But so do the stacks. I kinda like the look of all that aluminium stackage, but it should yell doesn't fit. I suppose you could argue form follows function. So if you have a stack it is to make it adjustable on the road, for which I have had the occasional need, but the big up is not adjustable, or fitted either. Double bad. But the real reason is it makes it look like a comfort bike.