All women know without having to ask or see. Women notice a telltale bulge in the man's pants, or they feel it while dancing. They also look at hand size and shoe size. Your wife or girlfriend may tell you that size doesn't matter but in my experience, women are at least interested in how "big" or "small" a prospective lover is. After all, if things work out, it's going to be inside them. Many times, my wife has noticed a guy with the telltale signs, and said something to me about it. It's not unlike how us guys love a nice set of tits, or ass, etc. They might be concealed by her clothing, but we still think about them and want to see them.