COSTA C-MONO RETAINER: The Costa C-Mono retainer is a high tenacity monofilament retainer with logo bead. The sleek and ultra-lightweight, flat, low-profile temple attachments ensure your sunglasses stay put, on and off the water. From end-to-end, the Costa C-Mono Retainer measures 20". The Costa C-Mono Retainer is compatible with all Costa sunglasses. VISIT THE COSTA BRAND SHOP: Click on the Costa logo above to view the entire Costa sunglasses and accessories assortment.