Installed on a 05 LTZ 400/455 with a Yosh RS3 system. I purchased this insert for the spark arrestor and the noise reduction was a huge bonus. I haven't measured the sound, but it’s a very noticeable drop. Installed in less than 2 minutes and works great. I primarily ride trails, so I'm not looking for the high end, get every ounce of power performance - my quad ran great. In short, this works as designed and described.