I'm getting ready to purchase the most expensive part of my RMH build, the roof kit and double walled exit flu. I've done some shopping around online and locally but I'm still kinda confused as to what I need.
I suggest you buy parts individually. I do not like the two piece roof jack they are offering, its another place of possible water leakage.That should be a one piece. Nor do I care for the cap, to restrictive in my opinion, I use a simple "coolie" cap on all my stoves.
I would go to Home depot /Lowes and price out individual pieces and see if you can do better than amazon.