I also want to say it's the skill more than the size. I have had small diameter cocks really hurt because the angle was wrong and jam into the sides of rectal canal. Cadence is also important...a little at a time, relax, the ring opens, go in more. I recently took the biggest cock (length and diameter) I've ever taken in fifty years of getting fucked and it was fantastic...a skilled escort who knew exactly what he was doing, went slow, and had me begging for more.