8GB (4GBx2) Team High Performance Memory RAM Upgrade For Lenovo ThinkPad T510 Series W500 Series Laptop. The Memory Kit comes with Life Time Warranty. at Amazon.com
SOLVED: Are 16GB RAM (2x8Gb) possible on my Lenovo T400? - Lenovo Laptop T400 - iFixit
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OFFTEK 4GB Replacement Memory RAM Upgrade for IBM-Lenovo ThinkPad W500 Series (DDR3-10600) Laptop Memory at Amazon.com