OWC 16GB PC12800 DDR3 1600MHz SO-DIMM Memory Compatible with 2015 (Late) iMac 27" w/ Retina 5K Models and Compatible PCs (OWC1600DDR3S16G) at Amazon .com
Amazon.com: Timetec 16GB KIT(2x8GB) Compatible for Apple DDR3 1333MHz PC3-10600 CL9 for Mac Book Pro (Early/Late 2011 13/15/17 inch), iMac(Mid 2010, Mid/Late 2011 21.5/27 inch), Mac Mini(Mid 2011) MAC RAM Upgrade :