If this is redundant I'm sorry, but anyway if you guys who are gettintg a HX40 turbo want to add a silencer ring(ever) you'll have to have the snap ring groove machined in as they don't come prepped for it(anyway mine didn't)--I will be in the process over the next few weeks of seeing if I can add one without having to remove the turbo & taking it to a machine shop---chris