I also ordered a set for my dually that I ordered. This is my third set of Duraflaps. I believe they are 14”. Here’s what they wrote...
Welcome back and thank you for order.
The DR20L 10 is the mud flap for the rear of your stock truck, and the DF12L 13/14 is the usual selection for the front. You can review these mud flaps on the following page:
https://duraflap.com/truck-model/dodge/duallys-dodge/2013-current-3500-dually/.
These are a drill-less installation, which means you do not drill any holes in your truck to install them. You do not need to remove your tires for installation, and they hang straight and centered to your tires.
They are designed to hang about 15" below the truck in the back and 12" below the truck in the front to give maximum protection for your trailer but leave room to avoid backing into the normal curb or parking guard. We do have shorter mud flaps for the front if you are concerned with being too close to the ground. We also have wider (14") mud flaps for the front for those looking for maximum protection or those with tires more than 11.5" wide. If you do have aftermarket wheels, tires or flares let us know right away.
If you have the optional hard plastic rear fender well liner you will have to either remove it or cut holes in it to attach the rear mud flaps. If you have the self-leveler system you may want to measure the distance below your truck to the ground to make sure these will be at least 6" off the ground to avoid backing up and pinching them between a curb and the tire. If these are too long we do have our shorter 2 wheel drive mud flaps that hang 12: below the truck.
It sounds like you may have that optional aftermarket liner. If so, you can either cut a hole in the liner to get to where the flat clip grabs the factory liner behind it. Or you can just drill a hole in the liner and use the bolt, nut washer without the flat clip. Hopefully the description of your truck that says fender well liner is only talking about the factory liner. Then none of this is an issue.
Our mud flaps are made from the finest quality materials available and are designed not to tear, peel, fade, rust or break. They are made from a 3/8" polyethylene/rubber blend; with anti-sail and anti-spray capabilities.
I have attached install directions and some photos for you to review.
Call them (541)245-9148