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
Tutorial: How to Upgrade T410/T420/400 Thinkpad Laptop to 8GB - YouTube
Upgrading Ram from 4Gb to 6Gb on Lenovo Thinkpad T420 - YouTube