Apple iMac 21.5" All-in-One Desktop Computer i3 3.07GHz 4GB Ram 500GB HDD Mac OS High Sierra MC508LL/A w/ Keyboard & Mouse
Install memory in an iMac - Apple Support
Amazon.com: Timetec 32GB KIT(4x8GB) Compatible for Apple DDR3 1333MHz PC3-10600 CL9 for iMac (Mid 2010 27 inch, Mid 2011 21.5/27 inch) SODIMM Memory Module MAC RAM Upgrade for iMac 11,3 / iMac 12,1 / iMac 12, 2 : Electronics
Apple A1311 iMac 21.5" Mid-2010 Intel i3 3.06GHz 4GB RAM 240GB SSD OS
A-Tech 8GB RAM for Apple MacBook Pro (Early/Late 2011), iMac (Mid 2010 27 inch 4-Core, Mid 2011 21.5/27 inch), Mac Mini (Mid 2011) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Module at Amazon.com
NEMIX RAM 32GB (4x8GB Upgrade) DDR3-1333 PC3-10600 204-Pin SODIMM Memory for Apple MacBook Pro Early/Late 2011, iMac Mid 2010 27 inch 4-Core, iMac Mid 2011 21.5/27” , Mac Mini Mid 2011 at Amazon.com
Apple iMac A1311 MC509LL/A 21.5-Inch 3.2Ghz Intel Core i3 8GB 1TB – WTS - Take off upto 65% on top name brands