Heatmaster ss chimney extensions

[Rocker4x4]

Wanting to maybe add a section or 2 to a heatmaster 10000e. In the book HM says Selkirk Ultra-temp, they come in 4ft sections and is pretty pricey! Selkirk also showd a Sure-Temp, it has same connections as ultra but is cheaper and 3ft sections. I read an old post on here that someone called Selkirk tech and they claim the only difference between the two is the inside material, said they both work great for wood, but the ultra is little more corrosion resistant to coal burning.. I don't burn any coal so im wondering if the sure-temp would work ok? Can anyone confirm this or have any input on it, thanks