A pair of polished aluminum, flared exhaust pipe tips.
They equal a real life 2-1/2" diameter.
The photo shows one tip on my .101" Aluminum Line as an example and the aluminum line is not included.
Use a very smalll amount of epoxy to secure the tip to the aluminum lin. Too much and it will spread out, possibly getting on the tip which you'll never get off.
A great technique is to drill a small hole in the center of the tip and exhaust pipe and inserting a piece of a straight pin or wire to 'pin' them together. This will make a much stronger bond.
Two aluminum tips, 1/25 scale.