We'll get to the specs in a moment, but first, a quick history lesson. After debuting the IntelliMouse in 1996, Microsoft continued to update the rodent for several years, up through 2003 when it released the IntelliMouse 3.0. That was the end of the line, until Microsoft resurrected the design in 2018 with a new Classic IntelliMouse.
"The Microsoft Pro IntelliMouse gives you a high-performance work and gaming-ready mouse with speed, responsiveness, precision, and durability. It features customizable buttons, a sleek look and feel, and a tracking sensor for the smallest flicks and largest gestures. Complete your experience by choosing a custom tail light color," Microsoft says.
In total, there are five buttons on Pro IntelliMouse, three of which can be customized (except in Windows 10 S for some reason). It's armed with a PixArt PAW3389PRO-MS sensor that can ramp up to 16,000 dpi, with a 12,000 fps refresh rate. For reference, the non-Pro version has a 3,200 dpi.