Derbedrossian is correct, they wear the paint to the point you can't take them off. Plus if you spend anytime on the bush roads the brush will clean the flares off on a regular basis.
Bottom line do not waste your money there more problems than there worth.
I had (still have in the junk pile behind the barn) Bush Wacker flares as mentioned above. They are expensive to purchase and to keep on the truck plus they do very little to protect the trucks finish.
Over time road crud builds up in behind them in the lower portions which also holds water. I had some nice blistered up rust areas when I took mine off.
I removed mine had the rusted areas repaired, then had the whole lower portion of the body including around the wheels were the flares had been Linexed in silver. It's the way to go. Looks very nice, tough as nails, doesn't cause any damage to the body, and doesn't get torn off by brush.