Selkirk 6" to 8" Damper Kit (Double Wall Stove Pipe - DSP)Selkirk 6" to 8" Damper Kit Must be installed directly on the stove's flue outlet where applicable. The "closed" position is still 20% open, so the venting system is not completely blocked. When handle is in the horizontal position, the damper is "closed" (reducing combustion). When handle is in the vertical position, the damper is wide open (no reduction of combustion). Allows the operator to alter the amount of air drawn through the venting system,