Duravent Piping adapter

I am looking for an approved adapter to go from a 4" Duravent brand pipe to 7 inch Selkirk Class A chimney. If there is an adapter that converts to standard 7" single wall stove pipe that would be even better. The purpose is to tie into my existing chimney rather than vent through the wall. Any thoughts?

I have one of these, what I need is to go from 4" pellet pipe (Duravent brand double wall pipe) to either 6 or 7 inch standard single wall stove pipe....thanks

http://www.ventingpipe.com/duravent...er-6-inch-with-4-inch-inner-diameter/p1762270

I used the same one as that (although the 8" size). If that is the correct one to adapt to his stove pipe, then he will most likely need these also....I went from 4" Duravent to 8" Metalbestos and Eric at Kinsman hooked me up with these part numbers, so the ones for 6 or 7" will be different (see part #'s in pics):

Thanks for your help and information.