16GB KIT (4 x 4GB) For IBM-Lenovo System Series x3400 (7973-xxx) x3400 (7974-xxx) x3400 (7975-xxx) x3400 (7976-xxx) x3400 (7978-xxx) x3450 (7948-56X) x3450 (7948-58X) x3450 (7948-x2X) x3450 (7948-x5X) x3450 (7948-xBX) x3450 (7948-xxx) x3500 (7977-xxx) x3550 x3550 (1913-xxx) x3550 (7978-xxx) x3650 x3650 (1914-xxx) x3650 (7979-xxx). DIMM DDR2 ECC Fully Buffered PC2-5300 667MHz RAM Memory. Genuine A-Tech Brand. 16GB KIT (4 x 4GB) DIMM DDR2 ECC Fully Buffered PC2-5300 667MHz RAM Memory Genuine A-Tech Memory Lifetime Warranty Toll Free Technical Support 1-866-557-4527 Designed For IBM-Lenovo System Series. (See Compatibility List Below)