Dude, what size do you wear -- 70 sizes available for you to choose from.

When buying clothes, you need to measure the three dimensions, but I've never heard of anyone buying underwear who needs to measure their, well, "dick size".

If clothes are a bit bigger or smaller, it's just a matter of showing a little more or less skin. But if the underwear doesn't fit, being a little small is not that big of a deal since they have enough elasticity (I still vividly remember the scene from "Days of Being Wild" where they blow up a balloon). However, if it's too big, then we're talking about whether it will fall down, leak, or even win a prize!