Samsung 4GB DDR3 PC3-12800 1600MHz 204-Pin SODIMM Laptop Memory Module RAM. Model M471B5273DH0-CK0 at Amazon.com
Samsung ram Memory Upgrade DDR3 PC3 12800, 1600MHz, 204 PIN, SODIMM for 2012 Apple MacBook Pro's, 2012 iMac's, and 2011/2012 Mac Mini's (16GB kit (2 x 8GB)) at Amazon.com
Samsung 4GB DDR3 RAM PC3-10600 240-Pin DIMM at Amazon.com