27.2 round

These Garmin Varia radar mounts are designed for a round 27.2mm seat post.  This size seat post is commonly found on road and gravel bikes with round posts.  This will not fit most mountain bikes as those posts are often larger.  They are shaped to perfectly conform to round profile and are very lightweight and durable.  They are available for both the Garmin standard radar unit and the Garmin unit with the integrated camera.