Product Detail A desktop memory kit, suited for upgrading system RAM Has a 1600 MHz clock speed, which is considerably more favorable than some similarly priced kits This kit has 4 GB of total memory You will need 2 open DIMM 240-pin slots to use this memory Be sure not to mix modules of different speeds if you already have memory installed. . The "G.Skill NQ Series F3-12800CL9D-4GBNQ Dual Channel - Memory - 4 GB : 2 x 2 GB - DIMM 240-pin - DDR3 - 1600 MHz / PC3-12800 - CL9 - 1.8 V - unbuffered - non-ECC" is best product for you. We recommended G.Skill NQ Series F3-12800CL9D-4GBNQ Dual Channel - Memory - 4 GB : 2 x 2 GB - DIMM 240-pin - DDR3 - 1600 MHz / PC3-12800 - CL9 - 1.8 V - unbuffered - non-ECC