27" iMac, late 2013 model. 24GB DDR3 RAM, 3.2GHz quad-core i5 processor. Operating system is Catalina (MacOS 10.15.7). Works great, I bought it refurbished two years ago and am now upgrading again. Comes with wireless Apple keyboard & mouse, brand new still in wrapping - came with my newer model but I don't need them. I also have the box & packaging to fit it if you want for safer transportation.