quite them down enough so i could here my music and take a phone call while rolling down the road . but they come with a cap in one end. with the cap they are too quite and i loose too much power and there was way too much back pressure that when i turned my bike off it would continue to run but the motor would run backwards . so after using a big drill bit 1"-1 1/2" wide , i drilled out the stupid cap and now they are perfect , just enough to quite the side shots down so i could hear my music and take a 