Installing: Easy. Finding the right one: a bit more work. I did drill a small hole in both the exhaust and dB killer and secure them with a small bolt, just to be safe. (Just make sure you're far enough from the raised edge so you can fit the hex bit of the bolt next to it.)
I bought these a couple of years ago:
https://shop.daniele-moto.de/artikelliste.aspx?su=reinsatz. I used them at a track day and they measured mostly between 85db and 95 dB. sometimes it went up to 100 dB, but probably then someone else close to me made more noise.
This week I bought another set (
http://www.desmorados.com/shop/catalog/product_info.php?cPath=332_358_294&products_id=865%3Cbr%3E) because I wanted a bit louder, and these seemed to have a bigger inner diameter plus they don't have the inner tube stick out the rear. The inner tube is actually helpfull if you want to pull them out with a vise grip, but I thought the new ones would be a bit louder, but they're not. I'm going to try and shorten them and see if I can get them a bit louder.
To find the right ones for your exhaust you have to look at the diameter of your outlet and the angle they make.