4GB 2Rx8 PC3-10600S RAM (Module Type: SO-DIMM (Small Outline Dual In-Line Memory Module) for laptops) Memory Generation: DDR3 (PC3) Speed: 1333 MHz (Data rate of 10666 MB/s, labeled as PC3-10600) Rank: 2Rx8 indicates Dual Rank, meaning it has memory chips on both sides of the stick and 8 chips per rank.