I'm currently rebuilding an old steel frame. After measuring it I was sure it'd take a 27.2mm seat post (see picture) so that's what i bought. Sadly it doesn't fit (despite some "encouragement" with a mallet). So I'm now in the position of needing to buy another.
Anyone got any suggestions on what size I should go for. You can see from the picture how it's measuring and I don't want to go wrong again.....