I had them resurfaced. There were no specs on the rotors. current thickness is 30.5 mm. The slots were removed on one of the fronts and partial removal on the other front. Backside slots are still present. I ran them for 20 miles then replaced with new girodiscs because the slots, or lack there of, irritated me. They are not warped. I had them resurfaced when i changed new pads just to freshen them up.