Spring heel fin straps are popular because they are comfortable, easy to use and practically indestructible. Highland premium spring fin straps are made from stainless steel springs and covered with nylon tube webbing to protect the spring and keep out grass and other plant matter. The thumb puller is streamlined and designed not to snag on objects like traditional finger loop designs can do. The springs have machined Delrin ends that attach to one of two types of stainless steel adapter fittings with a stainless screw and nylon lock nut. Nylon line on the inside of the spring prevents over-extension of the strap.