This is an old item and is being sold as a "junk item." The trackball and buttons function. However, the rubber ring for vertical scrolling has deteriorated over time and feels sticky. Please refrain from purchasing if you do not understand the above. Ergonomic design Logitech trackball mouse, with 5 buttons, uses AA batteries. - Brand: Logitech - Type: Trackball Mouse - Battery Type: AA batteries - Color: Gray - Number of Buttons: 5 - Features: Ergonomic design Thank you.