Hi, Thanks for your replies to my post. These covers do have the same affect as non marking tyres exept they only last for around 1 month and as a result are a lot cheaper. We sell our covers in the UK starting at £50 per set of 4 increasing to £70 for the largest size. Your right these are mainly for the rental industry and actualy a company in the US has been very successfull seling their covers. But they are restricted to making covers to fit each diferent size wheel. The name of the company is R+R surface protectors inc you might want to check out their website it has a lot of pictures and info about this certainproduct.
I look foreward to geting more replies.

Thanks Dave