Its 22 feet bumper to bumper

and I guess I should have said helps smooth air flow which it does as I have witnessed on my dads truck (an old F250) It basically keeps the air from dropping strait into the bed off the back of the cab and gives a pocket of about 2 1/2 feet behind the cab. When I go camping I cary a cooler and occaisionally a couple duffle bags on top of my tool box and at highway speeds the wind keeps messing with things and beating them all to hell even when they are tied down. We used to do the same on my dads truck and never had a problem cause the little spoiler worked just enough to prevent this problem. I'm not expecting extra mileage or any thing like that just don't have room in the bed once the bikes are loaded and had holes worn in one of my military duffles after just a few trips. I don't want the racer back style cause then I couldn't use the tool box.