If you make your own spear gun slings (bands) then you want to use only the best materials available. Having spare parts for your gun or sling is the only way to assure you won't get skunked on a spear fishing trip. JBL Pro Rings are made of durable Nickel Plated Brass for long life and superior strength. Rings are designed to anchor the surgical rubber tubing to the sling wishbone. Rings are used with the JBL641 and JBL642 Wishbones. Make sure you also have a few spare Wishbones to complete the job. Rings make a great Save-A-Dive Kit item.