Excellent Survival Tool for Scuba, Snorkeling, water sports or any outdoor backcountry sports. Shake back and forth for knocking noise, 6" long on a lanyard for attaching to your BC, vest, backpack or store in emergency gear bag. This tool has a neoprene case so no worries if you drop it in the water! Smoke free home. We want our customers happy: check out our photos and email us with any questions you might have. Thanks for visiting our site!