LED light is illuminated, and the entire optical fiber is illuminated by the light guiding optical fiber strip to achieve function. 7.The use of ultra ,Average battery life is 40 hours.(The product itself comes with 2 original button batteries)The battery can be replaced by itself, which is available at convenience stores or supermarkets. 8.These hats are size adjustable for a proper fit. Size: L（58-60cm） Adjustable Package Include: 1 x Hat Note：Please compare the detail sizes with yours before you !!! Colors may be slightly different depending on computer and monitor settings Please allow 1-3cm differs due to manual measurement, thanks (All measurement in cm and please note 1cm=0.39inch)Fashion design,100% Brand New,high quality! Season:Summer1.100% Brand New and high quality. 2.These are really cool hats! 3.Use them for party events, nighttime , sporting events, or just a regular hat during the day. 4.Glow Hats are battery and LED operated. They come with the first set installed and the batteries are replaceable. 5.GlowOccasion:CasualThickness:StandardGender: UnisexMaterial:Cottonhats feature 2 modes of operation activated by a small clicker inside the embroidering. They have a rapid flash, and steady on. 6.The