These are a heavy duty rubber mud flap. They are installed with a no body drill mounting bracket that has been inspected and authorized by the Ford Accessories program.
The gatorback flaps for the F-150 measure:
Front - 6.5" of tire coverage from bottom of the fender to bottom of the flap
Rear - 9.5" of tire coverage from bottom of the fender to bottom of the flap
This will be the same measurement on all trucks where they are stock or lifted. If you would like longer flaps there are 12x26 sizes available. This would add an additional 3" of length to each of the measurements
Yes, there are single rear and dually options available. Choose the logo you like and enter your vehicle info. The site will show you the sets for your truck