Can't seem to find this in the specs anywhere. Anyway, I need to fit a cheap Chinese tripod with a spirit level. I have a Gitzo series 2 tripod which has a spirit level attached to the bottom of the center column. *You can buy those bubble levels on ebay. The diameter of the center column on my Chinese tripod is 22mm. The ring on my Series 2 level is way too big, so, I know I need something smaller. The one for Series 1 would probably fit (possibly, with some modding) but I really do need to know the inner diameter (which would be close to the diameter of the center column). Alternatively, I would entertain a different (and better) solution for leveling my new tripod. Thanks!