Radians Flora Finder glasses are a helpful tool for field scouts and researchers, gardeners, or anyone who is interested in identifying plant stress in its early stages. Based on NASA technology, the purple filter mutes the green light rays reflected by healthy plants, allowing the discolored, diseased or stressed foliage to be identified before it's naturally visible. Flora Finders are the perfect low-priced alternative to similar glasses found at $60 or more. Do not drive or operate machinery while wearing this filter. ANSI Z87.1-2010 Certified for industrial impact protection.