A-TECH 4GB KIT (2 x 2GB) For IBM Lenovo ThinkPad R Series R61 R61e R61i. SO-DIMM DDR2 NON-ECC PC2-6400 800MHz RAM Memory. Genuine Brand. 4GB KIT (2 x 2GB) SO-DIMM DDR2 NON-ECC PC2-6400 800MHz RAM Memory Genuine A-Tech Memory Lifetime Warranty Toll Free Technical Support 1-866-557-4527 Designed For IBM Lenovo ThinkPad R Series. (See Compatibility List Below)