Patriot Memory Signature 4GB DDR3 SDRAM Memory Module For Desktop PC 4 GB 1 x 4GB DDR3 1600PC3 12800 DDR3 SDRAM 1600 MHz CL9 Non ECC Unbuffered 240 pin DIMM Lifetime Warranty - Office Depot
Kingston 4GB Module - DDR3L 1600MHz Server Premier - 4 GB - DDR3 SDRAM - 1600 MHz DDR3-1600/PC3-12800 - 1.35 V - ECC - Unbuffered - 240-pin - DIMM - KVR16LE11S8/4KF 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