I used to think that women had larger urethras than men because female catheters are larger. A post similar to this one caused me to do a bit of reading though. Women’s urethras are actually a little smaller on average. They can use larger stiffer catheters because their urethras are much shorter and almost straight. Men’s catheters have to be narrower because they have to be flexible to go through men’s longer curvier urethras.