The Kleen Wheels are fine by me.
Kleen Wheels are dust shields which protect your wheels from brake dust When I called the guy about the Smart, he said he was wondering when he'd get the first call about the new car. My dealer sent him a wheel for fitment and a couple weeks later I had a set.
The owners' manual recommends against dust shields, but that may be the $15 variety mentioned. The Kleen Wheels have "turbo venting" which should do an okay job of keeping airflow across the rotors and pads. I have different rotors and pads to augment the turbo-venting that may help mitigate any concerns Smart had over the use of the shields.
The front and back wheels are different but the one form works well in both places. The front is about flush with the spokes while the back shield is set back from the spokes at the wheel's edge, flush at the center. With my black painted rims (with bright edge) I love the look.
Many folks can get by with just the front pair since the disk brakes are what get most of the wear and since disks produce much more dust than drum brakes anyway. Any dust from the rear brakes doesn't have far to travel anyway, only affecting the wheels.
I'd suggest you get the Kleen Wheels, myself, but you might want to get one pair and see if you decide that the 2nd pair is worth the expense for the more consistent look though the protection is less helpful back there.
There may be some interference with balancing weights making it more difficult for a simple home install. If you can get them installed and rebalanced, the weights can be worked in there.
- John_H