Available Mud Flap Sizes & Applications- 12"x23" Cut Style - These are the "standard" of the Gatorback line of flaps and feature a "moon cut" look. They work best on the Front of most trucks and the Front & Rear of SUVs. 12"x23" Full Style - These Gatorback Mud Flaps have a rectangular or "full cut" look. They are best suited on the Rear of trucks and support or mounting brackets are recommended. 12"x26" Cut Style - Featuring a "moon cut" style, these flaps are best suited for the Front of taller or lifted pickup trucks. Off-set or kick-back brackets may be required for tire clearance. 12"x26" Full Style - Featuring a "full cut" style, these mud flats are best suited for the Rear of taller or lifted pickup trucks. Off-set or kick-back brackets may be required for tire clearance. 19"x24" or 21"x24" Dually - These flaps provide the best protecting for your dual rear wheel pickup truck. The 21" are 2" wider but also feature a heave reinforced bottom plate to help eliminate sailing and provide your truck years of protection on the road. The best way to determine if you should get the 19" or 21" wide flaps is to measure your trucks tire tread pattern. Most trucks require the 21"x24" for the proper amount of tire coverage. Mounting brackets are strongly encouraged on all dually mud flaps.