Most people know the difference between a flex-fit and an adjustable baseball cap, but they may not know the subtle differences. A flex-fit hat is made from one piece of material that is molded to fit your head. An adjustable hat has a strap in the back that allows you to adjust the fit.The biggest difference between the two hats is how comfortable they are to wear. A flex-fit hat will mold to your head and feel snug, whereas an adjustable hat will feel a bit more loose. If you are looking for a hat that is more comfortable and fits more securely, then go with a flex-fit. If you are looking for a hat that can be adjusted to fit different head sizes, then go with an adjustable hat.