but I'll ask them a few at a time. First off, I'm not new at burning, but I have absolutely no experience at burning PROPERLY. I bought this house 13 years ago and it came with the fireplace insert below. I know the glass is dirty - I know how to deal with that. I have no idea how old it is or what the model # is - only that it's a Grizzly. I haven't had much luck finding any info on the web about this thing. When I bought the house, the insert sat in the fireplace with an open hole on the top (no connection from the insert to the SS chimney liner). Lots of smoke, crappy fires and burned through wood like a campfire! I have since connected the insert to the flue liner (about 4 ft.) with flexible a SS piece. This cut down the smoke a ton! I burn occasionally and it seems like if I do everything right, I end up in my underwear - the thing puts out heat! However, these perfect fires are few and far between. Before I get too deep into the details, I have two questions: 1) Does anyone recognize this model and have any info on the age / quality of the unit (is it worth trying to mess with or should I consider a new model)? 2) I removed a large chunk of concrete-ish slab thing that sat on a shelf just below the exhaust hole because it was split in two. What was this, what does it do and is it replaceable? I hope you all will excuse my ignorance, but I have no idea what to do with this thing. I really enjoy the thought of having a warm, pretty, efficient woodburner to heat the house with, but I'd like not to waste my time and hard-earned $$$ on an endless project. I've scoured this forum for days and I'm convinced that I've come to the right place. I really appreciate any help / advice!!