I looked high and low for an old tractor tire rim for my own fire pit, but couldn't find one for a decent price! I checked out fire pit rings made by OK companies, but either they were too short (11" usually), or they were hideously expensive. In the end, I just fired up my welder and plasma cutter and made my own 16" high, 36" wide, ventilated hexagonal fire pit liner out of scrap sheet steel. Worked out nicely, and now I just need to get a load of round field stone to cement in place around the liner.