Caps are actually made up of a number of components.

Bill/Brim

* The brim protects your face from the sun
* They are usually made of PVC plastic, sewn inside some type of fabric

Buckram

* The buckram is the liner inside of the front of the cap that provides the structure and form
* Unstructured caps have no buckram, giving them the more casual, lower profile

Closure systems

* A closure system is the system on the back of adjustable caps that allows you to adjust the size
* Types of closures include plastic, Velcro, fabric snaps and leather bands

Embroidery

* Embroidery is the stitching that decorates the cap, usually in the front but can be anywhere

Eyelets

* Eyelets are the little holes scattered throughout the cap that allows your head to breathe
* They can either be metal or reinforced stitching

Panels

* Panels are the different pieces, usually six to eight, that make up the top of the cap