Superior Clay manufactures a complete line of vitrified clay flue liners from 3″ to 36″ diameters in round flue liners and from 4″x8″ to 24″x24″ in square and rectangular flue liners. Socket type joints and self aligning joints are available in round flue liners. Superior manufactures flues with holes, contoured flue rings, and flue tees. Flue rings are available in lengths from 4″ to 18.” FLUE SIZES TYPICALLY USED IN FIREPLACES: SUPERIOR CLAY FLUE LINER DIMENSIONS Rectangular Flue Lining Round Flue Lining Flue Lining with Opening Outside Dimensions (Approx. In.) Effective Flue Area (Sq. In.) Normal Inside Diameter (In.) Effective Flue Area (Sq. In.) Flue Lining with Opening Size of Flue (In.) Size of Opening (In.) 4-1/2 x 8-1/2 23 4 12 8-1/2 x 8-1/2 6-1/2 4-1/2 x 13 34 5 19 8-1/2 x 13 8 or 10 8 x 8 42 6 28 13 x 13 10 8-1/2 x 8-1/2 49 7 38 8 x 8 6-1/2 8 x 12 67 8 50 8 x 12 8 or 9 8-1/2 x 13 76 9 64 12 x 12 10 8-1/2 x 18 102 10 79 Flue Ring Tees and Flue Tee Sizes correspond to those regular flue and flue rings. Flue Measurements and Specs 12 x 12 102 12 113 12 x 16 131 15 177 13 x 13 127 18 255 13 x 18 173 21 346 16 x 16 181 24 452 16 x 20 222 27 530 18 x 18 233 30 706 20 x 20 298 33 829 20 x 24 335 36 989 24 x 24 431 SUPERIOR CLAY STANDARD FLUE RING SIZES 4 x 4 5 x 4 6 x 4 7 x 4 8 x 4 9 x 4 10 x 4 12 x 4 3 x 6 4 x 6 5 x 6 6 x 6 7 x 6 8 x 6 9 x 6 10 x 6 12 x 6 4 x 9 5 x 9 6 x 9 7 x 9 8 x 9 9 x 9 10 x 9 12 x 9 3 x 12 4 x 12 5 x 12 6 x 12 7 x 12 8 x 12 9 x 12 10 x 12 12 x 12 5 x 15 6 x 15 7 x 15 8 x 15 5 x 18 6 x 18 7 x 18 8 x 18 9 x 18 10 x 18 12 x 18