This is an electromagnetic wave shield knit hat made of special and superior silver fiber knit fabric. Knit hat cuts and blocks electromagnetic waves around the body at high efficiency to support a healthy body environment. Made of superior silver fiber knit fabric, this knit hat shields over 90% of electromagnetic waves around your head. Shields strong electromagnetic waves caused by smartphones, computers, tablets, Wi-Fi communication devices, microwave ovens, etc. Handling Instructions/Washing: Use neutral detergent (do not use weak alkaline detergent), hand wash with water, air dry (air dry in the shade), do not use fabric softener, do not bleach (chlorine or oxygen based or baking soda), do not iron, do not dry clean; Note: As with the silver fiber fabric, oxidation caused by air may be avoided, and the fabric color of the fabric may become dark, but it is normal oxidation phenomenon, but it does not affect the insulating effect of electromagnetic waves.