From Gear Scout:

Using their new online build tool, you can build a complete DD AR or just an upper. The website lets you point and click your way through the selection of barrel length, gas system length, hand guard, muzzle device, sights, bolt carrier group and fore end grip. At the end of the process you can order your gun, print a parts list and even get an image of your gun to share or use as desktop wallpaper while you wait for it to arrive. Daniel Defense tells me their goal is to ship custom builds within a day of receiving the order.