Microsoft Notebook Optical Mouse 4000--Dark Gray (B2P-00006) Microsoft High Definition Optical mouse products are more precise, more responsive, and deliver smoother tracking Point and click to enlarge and edit details using the Magnifier Scroll four ways for greater efficiency and comfort with 4-Way Scrolling Plug in the snap-in receiver when you're ready to work, then snap it into your mouse when you travel, preserving battery life Work with less interruption with longer battery life