Review on Garmin Seat Post Quarter Turn: Get the 010-10644-11 for Enhanced Convenience and Precision! by Douglas Jakab

This device is a very secure way to mount your Garmin Varia to your seat post. The only issue I had was that the rubber grommets that came with it weren't thick enough to securely attach it to my particular seatpost. I just found another piece of rubber in my shop and cut it to fit and all worked fine. You're looking to replace your stock Garmin mount with a seatpost that uses rubber straps as soon as possible. They age over time and eventually break and you lose a very expensive radar light. There is another brand of adjustable angle that I also got from Revain. It works well too, although this one is likely to be a little more durable and you pay a little more for that benefit too. I recommend each of them.