Work in comfort with a stable, sculpted trackball that supports your hand and lets you rest your arm. Logitech® Unifying receiver-the tiny, wireless receiver that stays in your laptop and lets you add compatible devices as you need them. With up to 18 months of use from a single AA, you might just forget your trackball uses batteries at all. Your trackball stays in one place, so you don't have to move your arm to move your cursor. Its sculpted shape supports your hand to let you work all day in comfort.