Hey Jerome
It is DDR3 1066MHZ memory, as far as i know you will be able to run a slightly higher frequency such as DDR3 1333MHZ, i would recommend it as it is around the same price and has the same latency but a slightly higher frequency. Brand wise i recommend Kingston, so maybe get 2 dimms of 4GB Kingston DDR3 1333MHZ. Try replace the 1066 that you currently have in there as the laptop will clock down the secondary module to the lower speed, and you will lose frequency.