I was told that the last dot was 6". I just measured my buddy, the Big Guy. If you measure to the center of the tip from the last dot, it is 6".
BTW, it seemed I lost a little depth when I went to a larger size dilator. The nurse said that is normal because everything has to stretch more. If you think about it, the depth is the same in the relaxed mode - as the sides are pushed out the bottom comes a little closer.
At over 11 months sometimes it slides right in and other times I have to fight for that last quarter inch. I start timing when I've finally got him in all the way and then keep a constant, firm pressure.
- Kate