I got an 8" flexible steel liner, same as the pipe opening on the stove. Our chimney is a rectangle 10" x 10.5" more or less. It should fit, fingers crossed. Luckily, we only need 15', and our roof is low pitch, easy to hop up on and walk around on. Never would have tried to DIY this project otherwise!
@coaly Ok, I've been scraping off the old ash and rust, and painting with Lowe's high heat paint. I finally figured out where that bottom air intake slot is you were talking about! I see it's about 1 3/4" high and 17ish" long. But I think I also have slots on the left and right. So I guess that means I pick one, either the bottom one or one of the sides, but not both?