4GB Crucial DDR3 PC3-12800 1600MHz CL11 1.35V Dual Memory Kit (2 x 2GB) by Crucial

DDR3L 240-pin DIMM
Desktop modules that operate at speeds up to 1600 MT/s and have a CL11 latency. It is dual voltage and can operate at 1.35V or 1.5V. It is Unbuffered and is non-ECC. It conforms to the industry standard UDIMM layout of 240 pins and is compatible with computers that take DDR3 UDIMM memory.

A dual inline memory module (DIMM) consists of a number of memory components (usually black) that are attached to a printed circuit board (usually green). The gold pins on the bottom of the DIMM provide a connection between the module and a socket on a larger printed circuit board. The pins on the front and back of a DIMM are not connected to each other.

Each 240-pin DIMM provides a 64-bit data path (72-bit for ECC or registered or Fully Buffered modules).To use DDR3 memory, your system motherboard must have 240-pin DIMM slots and a DDR3-enabled chipset. This is because a DDR3 SDRAM DIMM will not fit into a standard DDR2 DIMM socket or a DDR DIMM socket.