Lock-Top Damper Size(in) Fits INSIDE Flue Widths of(in) Fits INSIDE Flue Lengths of(in) Outside Base Dimensions(in) Height of Damper When Open(in) Cross Sectional Area of Opening(sq in)
8 x 8 6 - 9 6 - 9 10 x 10 8 49
8 x 13 6 - 9 1/2 9 - 12 1/2 10 x 13 8 1/2 70
8 x 17 6 - 9 14 - 17 1/2 10 x 18 7 1/2 105
13 x 13 9 - 12 1/2 9 - 12 1/2 13 x 13 9 100
13 x 17 9 - 12 1/2 14 - 17 1/2 13 x 18 7 3/4 150
17 x 17 14 - 17 1/2 14 - 17 1/2 18 1/4 x 18 1/4 7 1/4 225