In order to know the UV index, will be enough if you compare the colour that are in the central part of the quadrant with the 4 colours that are around; The 4 colours indicator go from the clearest to the darkest in function of the minus or greater intensity of UV rays: -Feeble intensity : UV index 1-2 (The protection is not necessary); -Mid intensity: UV index 3-5 (is necessary the protection: put a t-shirt, sun glasses, hat and sun protection); -High intensity: UV index 6-7 (is necessary the protection: Put a t-shirt, sun glasses, hat, sun protection); -Very high / Extreme intensity: UV index 8-9-10 / 11 + (avoid to be outdoors). -Product Material: Color Changing PVC