One size fits all adults, adjustable strap in back, cotton hat with silver underside liner. Deflects harmful EMF radiation from area of head covered by hat.
Silver lining fabric efficacy experiments :
WASHING & HANDLING INSTRUCTIONS: All Spero products use silver fabric which acts as a faraday cage. The silver fabric must be delicately handled if washed. Wash by hand with distilled water and gentle natural soap. Tap water or well water will ruin this fabric as chemicals in the water such as chlorine, sulfur and fluoride are corrosive to silver.