Chum's most innovative retainer designed to date, the harpoon design offers a versatile and stylish fit. The plastic harpoon system was designed to interact with different sized temples so that you can switch out easily and on the go. The Tideline and Tideline Adjustable will accommodate your glasses from a morning of fishing to hitting the afternoon trails with your pals. The interchangeable ends are made out of silicone so they will hold their original shape and not stretch out.