Samsung ram Memory 4GB (1 x 4GB) DDR3 PC3-12800,1600MHz, 204 PIN, SODIMM for laptops at Amazon.com
OWC 12GB (8GB+4GB) PC3-12800 DDR3L 1600MHz SO-DIMM 204 Pin CL11 Memory Upgrade Kit Compatible with iMac, Mac Mini, and MacBook Pro (OWC1600DDR3S12S) at Amazon.com