If you make your own spear gun slings (bands) then you want to use only the best materials available. The JBL Wishbones are made from high quality (302) stainless spring steel wire for superior strength, durability and long life. So, don't settle for anything less the JBL performance wishbones. The JBL641 Wishbone is for the 9/16" and 5/8" diameter Pro Series JBL Slings. Wishbones are a great save-a-dive kit item. Be sure to get a few JBL646 Pro Rings to complete the job.