Did that today with my Mitutoyo's. It's a carbon seatpost and the numbers were all over the place. Went from 31.4 to 31.7 depending on where I took the reading! Oh what fun. Too lazy to pull the post and measure the ID of the tube. Since I haven't seen a seat post offered in a 31.8 I guess it really doesn't matter at the end of the day anyway. I've only had the bike for 24 hours so I guess I'm better off just riding it at this point. It's supposed to be fun, why ruin it!@opimax, please feel free to disagree with me , someone else is the local dealer for Stromer in Austin. After doing a futile search on Stromer's site to confirm the seatpost diameter, then all @Kieren needs to do to resolve this question is look along the seatpost that came with the bike for a small set of stamped numbers. The one with a small circle with a vertical slash through it is your seatpost diameter. Given that most seatposts are scratched at the very least or somewhat greasy, check that number again after cleaning the post or use a set of calipers to measure the diameter.