Our Answer:

I am assuming that this measurement is the outer diameter? If so, this is indeed 7 inch diameter B-vent piping and can use the Metal-Fab Type B Round Chimney Pipe Storm Collar - For Chimney Pipes with a 7 Inch Inner Diameter and the Metal-Fab Type B Round Universal Chimney Vent Cap - For 7 Inch Chimney Systems. Both items are designed with flexibility in mind and can be used with numerous brands of B-vent pipe.

From Section Page: Type B Vent Pipe

ID: type-b-vent-pipe