Glad you asked! Never let anyone tell you a wig fits literally all head sizes. Everyone has a unique head shape and size. So although you may can get into a wig it doesn't necessarily mean it's a proper fit and a lot fail to realize this. Our ready to ship units will always go by the overall head circumference (21,22,23,etc.) so if your head circumference is a 22, which is average but you have a shorter than average ear to ear you will notice that the wig may actually fit but the ear to ear part may appear a little bulky. This explains why all measurements are required for a snug fit, otherwise going only by head cirfumference will only guarantee that it will fit.