12GB KIT 3 x 4 GB IBM-Lenovo IBM-Lenovo ThinkStation S20 4105-xxx 4157-xxx DIMM DDR3 ECC Registered PC3-8500 1066MHz Dual Rank RAM Memory Genuine A-Tech Brand 12GB KIT (3 x 4 GB) DIMM DDR3 ECC Registered PC3-8500 1066MHz Dual Rank RAM Memory Genuine A-Tech Memory Lifetime Warranty Toll Free Technical Support 1-866-557-4527 Designed For IBM-Lenovo IBM-Lenovo ThinkStation Series. (See Compatibility List Below)