4GB DDR4 2666 (PC4 21300) SODIMM Laptop Memory by NEMIX RAM at Amazon.com
A-Tech 4GB RAM for Apple MacBook Pro (Early/Late 2011), iMac (Mid 2010, Mid 2011, Late 2011), Mac Mini (Mid 2011) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Module at Amazon.com
4 MB Capacity per Module DIMM Computer Memory (RAM) 4 MB Total Capacity for sale | eBay