Thanks for the info on the rings but as it turns out I am simply retiring my PD and am very disappointed in the fact that there is all this charred would buried in the unit. At first I thought it must have been years of plant material that fell into the heat exchanger but considering one of the prior posts and banging the bottom of my unit out some more it is clear that this is charred wood in the unit. I am rather disappointed that I didn't notice this a long time ago. There are a ton of posts on the days experience. Is possible that this is the first time the charred wood issue has come up? I literally have black wood chips falling out of the unit when tapping it. Inhaling charred wood and soot sort of defeats the purpose of vaping. As much as I swore by my Days for many years in the end I am disappointed. Back to the MFLB and searching for a good days replacement.