DuraVent DVL Double Wall Black Stove Pipe Chimney Tools & Accessories Choose between the Flat Top Choose between the Flat Top Plate or the Terra Cotta Top Plate to seal off the existing flue from downdraft and weather Size Fits Inside Flue Sizes 8" x 8" 6" to 9" Width x 6" to 9" Length 8" x 13" 6" to 9 1 2" Width x 9" to 12 1 2" Length 8" x 17" 6" to 9" Width x 14" to 17 1 2" Length 13" x 13" 9" to 12 1 2" Width x 9" to 12 1 2" Length 13" x 17" 9" to 12 1 2" Width x 14" to 17 1 2" Length 17" x 17" 14" to 17 1 2" Width x 14" to 17 1 2" Length DuraVent DVL Double Wall Stove Pipe is used to reduce the clearance to combustible material from 18" down to as close as 6" from a wall and 8" from a ceiling please be sure to allow an extra 3 4" for overlap wherever double wall pipe sections will be joined together