Costa C-Line Retainer:: The Costa C-Line Retainer: features ultrathin, lightweight coated wire with logo bead to make sure your sunglasses stay put, on and off the water. From end-to-end, the Costa C-Line Retainer: measures 20". The Costa C-Line Adjustable Retainer is compatible with all Costa sunglasses and fits small to large temple tips. Born on the water in 1983: Costa Sunglasses for men and women is celebrating 40 years of making the premium sunglasses on the planet and protecting the watery world we call home