COSTA C-LINE LOOP RETAINER: The Costa C-Line Loop 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 Loop Retainer measures 20". The Costa C-Line Loop Adjustable Retainer is compatible with all Costa sunglasses. VISIT THE COSTA DEL MAR BRAND SHOP: Click on the Costa Del Mar logo above to view the entire Costa Del Mar sunglasses and accessories assortment.