4GB Upgrade for a Lenovo ThinkPad T420 System (DDR3 PC3-12800, Non-ECC, ) at Amazon.com
16GB KIT (2 x 8GB) for IBM Lenovo ThinkPad T Series T420 T420i T420s T520 T520i. SO-DIMM DDR3 Non-ECC PC3-10600 1333MHz RAM Memory. Genuine A-Tech Brand. at Amazon.com