Never had much of a problem going balls deep, although I've bottomed out my ex on several instances causing her pain, and once in a while pain for myself. It really just depends on the position. However, when we used toys she was usually able to take up to about 8" before having real pain, although once in a while she could the whole thing, IIRC 10", when she was super aroused and did a little move where it slid past her cervix. I can only guess it was situated in the A-Spot. We were just working up to a massive dong, like 12"x7.75", and was almost buried a couple times (using that little move of hers) when we started having problems.