Zan Headgear Gunner Convertible Photochromic Sunglasses BGUN001 Sleek and subtle convertible eyewear, which combines the most efficient aspects and functions of all eyewear available Wrap-around Grilamid TR90 frame can be worn either with smooth temples as sunglasses or with a detachable, adjustable strap as a goggle Vented removable closed cell foam prevents either lens fogging or wind and debris from distorting vision Photochromic lenses that change with altering light allow greater clarity, while rubber nose pieces create a lightweight, comfortable set of eyewear that allow you to truly enjoy the outdoor excursion of your choice The transmission rate for the photochromic lenses are 47% indoors and 15% in bright UV light