4GB KIT (2 x 2GB) For IBM-Lenovo ThinkCentre M Series M55 (8804-xxx) M55 (8805-xxx) M55 (8806-xxx) M55 (8807-xxx) M55 (8808-xxx) M55 (8810-xxx) M55 (8811-xxx) M55 (8812-xxx) M55 (8813-xxx) M55 (8814-xxx) M55 (8816-xxx) M55 Small (8800-Jxx) M55 Small (8800-xxx) M55 Ultra Small (8009-xxx) M55 Ultra Small (8799-xxx) M55 Ultra Small (8803-xxx) M55e (6490-xxx) M55e (6491-xxx) M55e (9279-xxx) M55e (9300-xxx). DIMM DDR2 NON-ECC PC2-5300 667MHz RAM Memory. Genuine A-Tech Brand. 4GB KIT (2 x 2GB) DIMM DDR2 NON-ECC PC2-5300 667MHz RAM Memory Genuine A-Tech Memory Lifetime Warranty Toll Free Technical Support 1-866-557-4527 Designed For IBM-Lenovo ThinkCentre M Series. (See Compatibility List Below)