Innovative engineering allowed us to create a ultra-small metal design that delivers your music with custom sound-no matter where your run takes you. Freedom 2 with speedfit is sweat-proof and fits right out of the box with an incredible Secure comfort-fit for any ear size. As the smallest wireless headphones ever, freedom 2 with speedfit has changed the game for runners who want the the perfect custom-fit for their wireless music experience. Features & details Secure-fit - you don’t have to Think about your ultra-small buds staying in while you run, no matter how hard you run Speedfit - switch to an Under-Ear fit in Seconds for easy access to the mic when a call comes in Sweat-proof - Double hydrophobic nano coated, sweat is a part of your routine, and freedom 2S sweat-proofing technology stands up to every drop of sweat you dish out Custom sound - pump up the bass - freedom 2 works with the Jaybird app to give you your music, your way with drop-free Bluetooth signal strength 8 hours in your pocket - you can run for hours without worrying about your battery life.Impedance: 16 Ohm