I measured the chimney as best I could and figure it to be approximately 28 feet. Since the difference in cost is only about 30 bucks, I'm ordering the 35 foot stainless steel liner and I'll cut off my waste. I called my stove manufacturer this morning and they told me there was no problem with reducing from the 8 inch outlet on my stove to a 6 inch liner. I just pulled my stove away and took a good look at it. the clay liner is something like 6x14 ??? that seems like a rather oddball size. I also wasn't too impressed with the job the sweep did a few weeks ago when he was here. I wtill have a substantial amount of soot on the outer sides of the liner. looks like they just ran the brush down the middle and didn't bother with the sides. Guess I can't reccomend that guy anymore. my damper opening is 6 inches but I might have to cut off the cast iron chunk sticking out that used to hold the handle open. So..What are the "gotchyas" that I should be aware of when installing this thing. I'm ordering a kit from one of the big name places. I'm thinking I should get some brushes and do a proper job of removing all the crap that's up there. The angle isn't too harsh to get the pipe thru the damper but I only have about 6 inches from stove top to the hearth opening...if that...so block off plate is gonna be a pain. Any suggestions?