2pc of 4GB PC3-10600 CL9 16c 256×8 DDR3-1333 204pin SODIMM. Genuine CMS brand, CMS is one of the most trusted names in the Computer Memory industry and this product carries a Lifetime Warranty from CMS. Compatible with: Compatible with Dell VOSTRO 1540 Maximum Memory: 8 GB SOCKETS: 2 MODULES MUST BE ORDERED AND INSTALLED IN PAIRS for Dual Channel mode, if supported. If 4GB is installed, the recognized memory may be reduced to 3.5GB or less (depending on system configuration and memory allocation). Maximum configurations require a 64-bit operating system.