Mine were fitted to a set of DP carbon cans on my ST4S. They were the 50mm ones. They are held in place by an allen bolt from underneath and you have to measure where you have to drill a hole in end of the can. Simple to do if you take your time (measure twice cut [drill] once). They significantly reduce the noise. Measure your outlet to establish the sizing you require. I have now sold the cans so I can't show you a picture of them in place.