OMG....500 would be good for a 93 Cobra owner with dirt low miles, but guys like us with say average cars aren't gonna pay that. I had minimal surface rust on my 81 notch fenders...just on the lips. I ground that crap off with a grinder, then striped the entire fender. I POR15ed the whole inside of it, then primed it and painted it. I primed, sealed and painted the outside obviously as well. Still looking good!!!!