This is the Hammerhead Spearguns Heavy Duty Bungee/Shock Cord for Speargun Features: OD rubber - 7/16" ID rubber - 3/16" Dynema braided 2.0mm - 800lbs tested HammerHead Premium bungees are the same ones used on our Evolution Spearguns. Made with a special heavy duty 1/2" rubber tubing and strung with a nylon coated dyneema with ~600 pounds of breaking strength. Designed for the biggest fish under the harshest most extreme conditions.