Costa Del Mar Blackfin 580P Lenses You might have gallons of brine in your face and 600 pounds on your hook, but these sunglasses still wont slip. The Hydrolite co-injected lining takes care of that, and the flexible frame means serious comfort. Blackfin pushes the edge in sunglass performance--so you can push it everywhere else. Features: Comfortable medium fit. Stainless steel integral hinge. Durable co-injected nylon frame. Includes hard case. 100% UV light blockage for max protection. 100% polarization kills reflected glare and reduces eye strain. Built by hand and backed for life. Every pair of Costas include a lifetime warranty. Plastic lenses are lightweight, impact- and scratch-resistant.