Help me cap my chimney - I think duravent brand...

I bought my house with a stove in the carriage house. The contractor for the seller put a new chimney on but at some point the cap went missing. It looks like a Duravent brand to me. The outer diameter is a little less than 8" and the inside of the double wall pipe is about 6" diameter. The only thing keeping me from getting an 8" diameter duravent cap is that there are these 4 "L" shape tangs that are spot welded on. You can kinda make them out in the picture but they are across from each other and equidistant from each other around the perimeter at the top. Is that something that is supposed to be there or do I grind those off and just thread a duravent cap on?

PS dont mind the shanty cap on there - i just stuck that in the chimney to keep water out of the stove.

Thank you. So what is currently on the pipe threads off? That would make a lot of sense if so! And if I understand you correctly I need a 6" cap that threads on?