Beal's Air Force Three Belay Device adds a small change to the modern tube device that drastically reduces tension to your climbing rope. It has a unique notch at the back of the device that helps the rope slide through the device at a less harsh angle. V-shaped grooves give proper friction whether you're belaying with a skinny twin rope or a thick single rope. The Air Force Three also allows auto-locking belays from climbing anchors, and the small hole helps you give slack to your second.