The Klim Muffler Sunglasses inspire an iconic frameless lens style - offering a clean and broad FOV, fatigue-reducing lens technology and a comfortable, adjustable fit for all-day wear. A lightweight, durable and flexible frame combines with ergonomically optimized rubber grip pads to keep the Mufflers locked in all day long. TR90 thermoplastic lightweight semi-flexible frame material. Textured rubber nose and temple arm pads for grip. Removable interchangeable molded rubber nose bridge for fit adjustment. Low-profile flexible temple arms. Compatible with RX clip (sold separately) for prescription eyewear. Metal injection-molded (MIM) 316L grade stainless steel hinge mechanism. Lens color optimized for dynamic visual acuity reduces fatigue. Polycarbonate hard coated anti-scratch frameless lens. Super HD lens clarity is optically correct, reduces eye fatigue.