15-23 in. Telescopic Flat Roof Jack 

The flange can flex from flat to a 1/12 pitch

This roof jack is essential for venting an 80% efficient mobile home gas furnace. To ensure a proper fit, measure the distance from the base of the furnace to the roof flange, then subtract the furnace's height from that measurement. Choose a roof jack that can telescope within this range for a precise fit. For adjusting the roof pitch, check the accessories for the suitable roof wedge.