Furnace Flue Vent Adapter

A furnace flue vent adapter was needed for a 4" - 6" transition. Only this adapter looked like a duct adapter. The only information on the label was L-R54 which I can’t seem to find any information on. Does anyone have any idea what I’m looking at here?

All adapters should utilize the same method of attachment such as a twist and lock connection. At the very least I’d call out the tape and have it repaired by a HVAC contractor. Not sure why it’s increased, may have had another fixture attached at some time.

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Long, Round/Reducing 5"x4" (L-R54). Most likely single wall HVAC duct adapter. Needs to be b-vent for a gas furnace. What did it look like from the top? Also, the vent has to be sized correctly all the way. Increasing the size can contribute to condensation (followed by corrosion) and improper draft.

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