34mm, and if you measure them, they are 33.9mm.

I think the frame crack issue is not necessarily elated to non-stock seatposts since at least one case that was reported had the stock post; however please note that the seatpost is a structural member of the frame and is therefore part of the frame structural integrity. The bike cannot be ridden with a short post stuck in the upper portion only - that will lead to the frame cracking.