Samsung ram Memory 4GB (1 x 4GB) DDR3 PC3-12800,1600MHz, 204 PIN, SODIMM for laptops
OWC 8GB (2 x 4GB) PC12800 DDR3L 1600MHz SO-DIMMs Memory Compatible with 2011-2015 iMac, 2011-12 Mac Mini, and 2011-2012 MacBook Pro (Non-Retina Display) Models (OWC1600DDR3S08S)
ADATA Premier DDR3 1333MHz 4GB Memory Modules (AD3S1333C4G9-R) at Amazon.com
NEMIX RAM 4GB Replacement for Samsung M471B5273EB0-CK0 DDR3-1600 SODIMM 2Rx8 at Amazon.com