Lining is used to give a better shape of cap. Lining is often laminated onto the front 2 panels. If the cap has laminated lining, it is not ideal to machine wash. This is because air bubbles may develop between the front panel and the lining panel. Picture shown is Cotton lining. Appearance resembles as Nylon lining. Cotton lining is a little bit cheaper but not as stiff as Nylon lining.