SIZE – Small fits for 55-56CM 21.6″-22″; Medium fits for 56-58CM 22″-22.8″; Large fits for 58-60CM 22.8″-23.6″. With an adjustable tape built in sweatband to assist to find the most efficient are compatible.
FOLDABLE: packable, crushable, NO crease! Great for cruise, commute, gardening, boating or beach vacation.
SPF: passed UPF 50+ test, the 3.7″ wide brim may block so much sun UV rays.
DETACHABLE CHIN STRAP: adjustable for a snug are compatible; would possibly not blown off when it gets windy.
VENTILATED: best possible for beach vacation, also great for summer rides, fishing and climbing.