W505G Cozy Gravity Dual Wall Furnace 50K BTU  Dual wall models provide economy and flexibility of operation and allow individual temperature control in “hard-to-heat” areas. Cozy is a perfect answer for either new construction or remodeling heating applications. Specifications: Dual Wall Furnace with 1/2 inch gas inletType Gas Natural BTU Input per hour 50,000  Vent Pipe Opening 4"Finished Dimensions: 16-1/2" W x 68-3/8" H x 6-1/2" *Model W505G replaces model W505F