This cooling skull cap has a tie back to ensure close fit to head. Activates Instantly with a snap when wet. 1 minute activation. 30% Cooler then your skin. Anti-microbial – treatment to prevent growth of odor causing bacteria. Environmentally friendly mesh drawstring bag for washing & carrying with you. One size fits most. Run under ice cold water, snap when wet and re-do if you feel the cooling wear off.