Plastic all the way. I've had my rails dented despite the aluminum skidders on other KTMs & Huskys. So far, knock wood, my 2009 EXC has none, not that they seem to matter anyway. I would think the plastic might prevent dents more anyway by transmitting less thru them. If that concerned, try a strip of thin foam between the rails/plate to absorb hits more. I'd try more "give" rather than a stiffer, harder material.