Random Orbit Action. Researched and developed for ultra-fine finishing. Flex-cover gives comfortable grip, prevents stiff fingers. Low profile, vibration-free motor insures full contact sanding. Unique air efficiency system. Positive-action drive supported by 4 special bearings generates more power on less air. Over-size drive head eliminates pad wobble for full contact sanding. New positive air-control valve. Built-in pad release feature