Very tiny.  Even smaller than a mac mini with way more performance for the comparable price.  Included Windows 10 which we installed/patched.  Also bought a 4k monitor using the display port text looks fantastic.  Everything works fast and and neat with wireless keyboard/mouse (also bought separate).  Plenty of power for what we need to do (video conferences, office applications, web browsing, etc)  Highly recommend for virtual learning or work from home environments where space is premium.