Baseball cap fabric has elastic cotton,cotton is used because cotton is more comfortable and friendly to skin,strong moisture absorption.
The straps are elastic,which can be made to fit more people's heads,or Velcro,metal or plastic fasteners that can be adjusted to fit all types of people.
What front page interfacing cloth USES is the Oxford cloth that does not change shape mostly,
embroidy very delicate also.
washing : Regular hand washing, the general hat will not shrink.
Wash with about 30 degrees cold or warm water. Don't wash your hat too hot,or it will shrink.
It is best to wash your hat with soap,not with washing powder.