I bought this post in order to fit a large banana seat on a new 26" Trek mountain bike. The post is lightweight and it installed easily. The bottom of the post is 27.2 mm, but the top is slightly smaller (25 mm?), which allows for installation of older bike seats using the standard clamp that is attached at the bottom of those seats. This was the only seat post of this size and type that I was able to find without spending too much time online. None of the online aftermarket bicycle parts stores I found carried a similar seat post with the same dimensions.