16GB UPGRADE, 2X8GB DDR3L-1600MHz PC3L-12800 SODIMM for Apple iMac 21.5" Late 2013 Intel Core i7 Quad-Core 2.9GHz 3.1GHz ME087LL/A, intel Core i5 Quad-Core 2.7GHz 21.5" ME086LL/AIntel Core i5 Quad-Core 2.7GHz 21.5" ME086LL/A, (iMac14,1) . Apple recommends installing memory in matching pairs for best performance. Additional Details ------------------------------ Package quantity: 1