Boots REACTOLITEâ„¢ Sunglasses Photochromic Black 100% UVA UVB 6409431. Boots Reactoliteâ„¢ sunglasses in a sleek brown tortoise shell design, featuring cutting-edge photochromic lenses. Experience the ultimate in eye comfort as these lenses automatically adapt and react to changing light conditions, gradually darkening when exposed to sunlight.