I would like to remind people purchasing trucks that it is a state law to have mud flaps in the rear wheel well. Montana uses a lot of gravel in the winter to keep our roads safe and is just a basic Montana courtesy to have mud flaps on your vehicle to help prevent windshield damage from flying rocks to vehicles behind you.
See Montana Code 61-9-407 which basically says all trucks, truck-tractors, trailers or semi-trailers moved on the highways of Montana shall be equipped with fenders, splash aprons or flaps designed, constructed and attached to the rearmost wheels or set of wheels so as to arrest and deflect dirt, mud and water, rocks and other substances that may be picked up and thrown into the air by the rear wheels. If the vehicle is in excess of 8,000 pounds gross vehicle weight, such fenders, splash aprons, or flaps shall extend downward to a point that is not more than 10” above the surface of the highway when the vehicle is empty.
Dugan Reber, Whitefish