The Dixettes getting chilly 
She went to Home Depot, and picked up the double wall chimney, but couldn't find a double wall elbow.
Do they make a double wall elbow ( I've seen one, I think), and if they do, are brands interchangeable, say Duravent & Selkirk?
Or, can we mix a single wall elbow, as long as clearance to combustibles are met?
We're talking on the Timber Ridge.

She went to Home Depot, and picked up the double wall chimney, but couldn't find a double wall elbow.
Do they make a double wall elbow ( I've seen one, I think), and if they do, are brands interchangeable, say Duravent & Selkirk?
Or, can we mix a single wall elbow, as long as clearance to combustibles are met?
We're talking on the Timber Ridge.