The Fingertip Mini Mini USB Trackball from Japan’s Donya is just that- a tiny little trackball. Windows compatible, this is a full function trackball style mouse. I’m not sure how accurate or easy it is to use this since the trackball is so small. This might be the smallest trackball mouse ever produced? I’ve certainly not seen a smaller one. Personally I couldn’t use this since I had burn off all my fingerprints after an “incident” in the late ’90’s.