The Halo from Key by JOPEN is a c-ring designed to keep an erection harder while providing vibration to the wearer and a partner. 5 patterns. Silicone. Uses (1) AAA battery. Waterproof. One year warranty. Soft, lint-free pouch included. 1.25"D Looking to reduce your environmental footprint? Check out the Ela, the Halo's rechargeable companion!