RealTruck carries a great selection of custom door sills your 2018 GMC Sierra 3500 truck. View the top brands in door sills you need to customize your GMC pickup. RealTruck carries stainless steel, billet aluminum, diamond plate, and illuminated door sills for your 2018 GMC Sierra 3500. We also offer free, fast shipping, and the best customer service you can find. Shop now or give us a call at 877-216-5446.