BabyMocs Sunnies Yellow comes in one size (we have seen everything from a 3 month old - 13 year old fit in them). See reference pictures to see how they fit on different head shapes.
They are made out of recycled plastic and have a 100% UV-protection with a UV400 lens. UV 400 is the category which blocks all light rays with wavelengths up to 400 nanometers. This covers all of UVA and UVB rays.