4GB DDR3L Low Voltage 1600 MHz (PC3-12800) CL11 SODIMM - Notebook RAM | Dell USA
Nanya 4GB DDR3 Memory SO-DIMM 204pin PC3-12800S 1600MHz at Amazon.com
OWC 4GB PC12800 DDR3L 1600MHz SO-DIMM Memory Compatible with 2011-2015 iMac, 2011-12 Mac Mini, and 2011-2012 MacBook Pro (Non-Retina Display) Models (OWC1600DDR3S4GB) at Amazon.com