OFFTEK 4GB Replacement Memory RAM Upgrade for IBM-Lenovo ThinkPad T420 (DDR3-12800) Laptop Memory at Amazon.com
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How to Upgrade 16gb RAM & SSD Caddy 9.5 mm Lenovo Thinkpad E570 Disassembly - YouTube
Lenovo ThinkPad T420/T420i - iFixit
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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
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
NEW 16GB (2X8GB) Memory for Lenovo ThinkPad T420s 4170, 4171, 4173, 4174 DDR3 | eBay
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