My seat tube was 30.4mm and my new dropper post is 30.9mm.I got the size slightly larger and it worked great. I used WD40 and that made a mess and probably made things worse.I ended up using a sanding/sander eraser after some passes to clean the honing tool.It took a while, like a long time, but I test fit and test fit until it slipped in
Rating: [5 of 5 Stars!]