Product details:

4 inch X 12 inch ADJUSTABLE PELLET VENT PIPEAdjustable double-wall pipe adds 3-10 inches of additional length to rigid vent pipe - Stainless steel inner wall with galvalume outer wall for corrosion resistant - Not to be with corn burning stoves which require multi-fuel pipe systems - Must have required 3 inch clearance to combustibles - Includes 1/4 inch screw for securing pipe