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.
240-pin DIMMs are used to provide DDR2 SDRAM memory for desktop computers. DDR2 is a leading-edge generation of memory with an improved architecture that allows it to transmit data very fast.

To use DDR2 memory, your system motherboard must have 240-pin DIMM slots and a DDR2-enabled chipset. A DDR2 SDRAM DIMM will not fit into a standard SDRAM DIMM socket or a DDR DIMM socket.
RS 774-3085 Kit contains 2 x 1Gb 800Mhz DDR2 memory modules