I love my stacks, I have five inch curved stacks and get thumbs up every where I go. I can't believe how with the window's up, it's quiter in the cab. I just put them on about two weeks ago and right after I did, a guy here at work powerstroke lost it's brakes so we went and got his flat bed trailer and on they way back to his house I made sure that I puffed a little black smoke at every Powerstroke I passed. It was cool to see the rolling smoke in my sideview mirriors.