The OWC / Other World Computing 4GB DDR3 1333 MHz SO-DIMM Memory Module provides 4GB of memory for your Mac or Windows systems, such as notebooks and ultra-compact desktops. This addition or upgrade of memory enables your system to run more applications at the same time and render large-sized images. For performance, this DDR3 memory module features a speed of PC3-10600 (1333 MHz) and a timing of 9-9-9-24. Additionally, OWC has designed this dual-ranked module with a 204-pin SO-DIMM form factor and to run on 1.5V.