mt vernon adapter

Can someone point out the correct stove adapter for using simpson duravent pro? I have been having exhaust leak for the past year and a friend thought the adapter - first piece to connect to the stove was too large.

Thanks

The one I have has about a quarter inch gap all around. Not sure if that is typical or not.

Just an update. I ordered a new duravent pro 3 inch adapter and it fits correctly. The part is 3pvp-ad and it fits tight compared the old adapter that was leaking. The previous "adapter" i was given was so loose I was not able to put enough sealant on to close it. It was pretty much an extension of the outside diameter of the duravent pipe where the new adapter decreases down to fit the stove. I ended up crushing the 12 inch piece of pipe that goes through the thimble trying to get the old adapter off. I will have to order a new one. Does duravent offer a 14inch pipe or an extendable section of pipe? The reason is that the wall is about 8" thick and it makes the stove fit tight against the wall and difficult to work with. I picked up some Rutland RTV clear sealant to seal the new adapter with. When I go to put the new adapter on how far do I slide it onto the Mt. Vernon? Also, should I put the adapter on first and then connect the pipe through the wall or put the wall pipe and adapter together and then on the stove through the exterior wall? I suppose it does not matter but I want to do it right this time. I wanted to get you guys pictures of the old adapter but I crushed it trying to get it apart.

Thanks, Matt