Great sound, deep loud hum I wished for a 1972 442. The Flowmaster website says it's not recommended for road vehicles. They're loud, but I don't feel like they're too loud for street use. I personally think the Flowmaster is doing themselves a disservice by saying that Super 10s are not meant for street use. The sound they produce is exactly what most muscle car enthusiasts are looking for. I replaced the Flowmaster 40 with a Super 10 and wish I had bought a Super 10 to begin with.