Full Details from Amazon.com : http://www.amazon.com/gp/product/B00BFGG3OA?tag=onigi-20

8GB 2X4GB Memory RAM for Dell Studio Laptop XPS 1640 204pin 1066MHz PC3-8500 DDR3 SO-DIMM Black

Brand new certified 204pin PC3-8500 1066MHz DDR3 SO-DIMM Black Diamond Memory
Low density 8GB 2X4GB memory kit 2 sticks of memory module dual channel supported memory module
100 compatible garrantee for Dell Studio Laptop XPS 1640
100 pre-tested on Dell system to ensure functionality
Lifetime warranty