The hole is 127mm, it's just the collar that is slightly bigger.Having re read the earlier posts, I did, in fact, see the above. Since then, about 5 mins ago, I have been googling and returned with some info - and saw your exasperated response.
I found that your stove has a "V125 burner", which suggests a 125 flue. And you are correct, the MI's are pathetic, assuming that what I found is what you received.
However, as I said earlier, the general rule and general wording (and this is an excerpt pulled from anther MI) is that "The flue size (diameter or cross sectional area) must not be smaller than the size of the stove outlet."
Cmarkr may well be correct, and probably is, as he appears to run a showroom. I would not be happy assuming anything in this business, and would be seeking written clarification from the supplier. I would not be happy relying on MI's applicable to similar products, although we all know a lot of stuff IS the same but re-badged.
I suppose this is one of the problems with dealing with Chinese stuff. I ran a showroom for 20 years, and one of the worst, professionally, suppliers was Gallery, selling a lot of Chinese gear, and I believe they are the importers for Tiger. We did not deal with them for long.
Its mad that we are still using fire cement and rope for these when boilers are using seals and washers! Surely fires could be a lot better made with specific flues made by the manufacturer rather then just using universal ones.