8GB Stick 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
Renewed) Lenovo ThinkPad T420 Intel 2nd Gen Core i5 14 inches Business Laptop (4 GB, 500 GB, 1366x768, LED, Windows 7, Integrated Graphics, Black, 2 Kg) : Amazon.in: Computers & Accessories
How to Replace or Upgrade RAM Lenovo T420 - YouTube