Factory Firestones with 17k miles on them. I noticed this the other day while doing some Spring cleaning of wheels. I'd really rather not replace tires right now, but I also want to be safe as we tow a 35 foot 5th wheel and the last thing I want is a blowout. It may be difficult to tell from the photos but the length of the cut is approx 1/2 inch. Depth does not appear to go into any of the sidewall plies. Under the black sidewall there appears to be a layer of white rubber that you can see in one of the photos.