Not like a regular trackball mouse, Genius NetScroll+ Eye is a lightweight mouse that doesn't use a mouse ball. It uses an optical sensor and digital signal processor to read and follow your mouse movements. Plus it eliminates erratic cursor movement and dust accumulation. Enjoy enhanced features like the optical engine for stable and accurate cursor movements, Magic-Scroll for fast browsing on the Internet and Windows documents, and program the buttons to assign popular step-saving shortcuts.