Upgrading Ram from 4Gb to 6Gb on Lenovo Thinkpad T420 - YouTube
CMS 16GB (2X8GB) DDR3 10600 1333MHZ Non ECC SODIMM Memory Ram Upgrade Compatible with Lenovo® Thinkpad T420 4177, 4178, 4180, 4236 Series - A13 at Amazon.com
Lenovo ThinkPad T420 14.0" Standard Used Laptop - Intel Core i5 2520M 2nd Gen 2.5 GHz 4GB SODIMM DDR3 SATA 2.5" 320GB HDD DVD-RW Windows 10 Home 64-Bit - Walmart.com
Notebooks - What's this slot on T420 | bit-tech.net Forums
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
Refurbed this T420 for a local DJ, 16GB+512GB SSD and a fresh copy of Windows 11. Good to go for another 10 years! : r/thinkpad