31.6 -> 27.2
I got this to fit a different seapost in my BMC. The lip that shows right where the seatpost is inserted is not very noticeable unless you are right down looking at it. Weight was light in my opinion for the size. This size was made of a lightweight rubber, not aluminum. I've got a carbon seatpost in there and it isn't slipping around any. I suspect that the rubber material may help a bit with protecting the carbon from small amounts of overtightening if you aren't using a torque wrench, and it may kill off some more vibration, but those ideas are probably just wishful thinking.