I don't know if you bought already one.
I have this one pictured, it is a 27.2 mm, 230 mm long.
Has some ugly marks and at the insertion end is like somebody bite it (not mines).
That end is a little oval, going from 26.96 to 27.28 or so.
maybe you can cut a little and make it look better, even that part goes in the seat tube.
let me know if you are interested.
18$ shipped
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1992 Torelli Nitro Express; 1972 Claud Butler.