In short, 204-pin Small Outline Dual Inline Memory Modules (SODIMMs) are the form factor used to provide DDR3 memory modules for notebook computers & other small form factor computing platforms. 204-pin SODIMMs are currently available in PC3-8500 (DDR3 1066 M Hz) & PC3-10600 (DDR3 1333 M Hz) speeds. To use DDR3 memory, your system must have both a 204-pin SODIMM slot & a chipset that supports DDR3 memory. A DDR3 SODIMM will not fit into DDR2 or DDR memory sockets. (Information about which memory technology your system uses is included in the Crucial Memory Advisor tool). SODIMMs are smaller & thinner than regular DIMMs, & the 204-pin SODIMM PCBs are always 2.6 inches long & are usually around 1.18 inches high (though the heights can vary slightly). They consist of a number of memory components (usually Black) that are attached to a printed circuit board (usually Green). The number of memory components on a 204-pin SODIMM's Printed Circuit Board (PCB) can vary, but the PCB will always have 102 pins on the front & the back both, for a total of 204 pins. The gold pins on the bottom of the SODIMM provide the connection between the memory module & the memory socket.