DDR3 204-pin SODIMM: Approximately 2.66 in. by 1.18 in. (66 mm by 30 mm)
In short, 204-pin small outline dual inline memory modules (SODIMMs) are the form factor used to provide DDR3 memory modules for notebook computers and other small form factor computing platforms. 204-pin SODIMMs are currently available in PC3-8500 (DDR3 1066MHz) and PC3-10600 (DDR3 1333MHz) speeds.
To use DDR3 memory, your system must have both a 204-pin SODIMM slot and 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.)