Just installed Roush axle backs yesterday never heard them in person but pulled the trigger anyway. Took about 40 mins the hardest part was getting the driver side sleeve into the rubber grommet real nice tight fit and very high quality. They sound outstanding, very deep growl especially after about 2500 rpm.My only complaint is that they are very loud under heavy acceleration. I think it just a matter of time before I get stopped, The cops around here are pricks. We will see I may have to sell them for something a little quieter.