The Flares are made from SMC. Fiberglass won't work on them, you have to buy SMC resin. There are 2 different drivers side flares as well. When I was "building" my dually, I found a complete long box with better flares than mine, but the sheetmetal was trashed. When I went to put the drivers side flare on, I had to drill new holes on the front edge a couple inches back to get it on. It covered the old holes, but it was 100% shorter. I don't know what year the box was I bought but it was a long box.