Stove pipe vs Class A chimney
Stove pipe (chimney connector) is single- or double-wall pipe that connects the stove to the chimney and may only run through open room space; Class A chimney is insulated, listed high-temperature pipe that carries the flue through ceilings, attics, and roofs. They are different products with different clearances and are not interchangeable.
Single-wall stove pipe typically requires 18 inches of clearance to combustibles (double-wall less), and it must never pass through a wall, ceiling, or window. Where the flue penetrates the structure, listed Class A chimney — or an existing code-compliant masonry chimney with a proper liner — takes over.
Chimney height and termination follow the "10-3-2" style rules in NFPA 211 and the stove manual: at least 3 feet above the roof penetration and 2 feet above anything within 10 feet. A short or under-sized flue is the most common cause of poor draft complaints.