2pcs of 4GB PC3-10600 DDR3-1333 16c 256x8 204-pin SDRAM 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 Max Memory: 4 GB using a 32-bit Operating System 8 GB using a 64-bit Operating System Sockets: 2 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. Compatible with: HP/Compaq ProBook 4435s HP/Compaq ProBook 4436s HP/Compaq ProBook 4520s HP/Compaq ProBook 4525s HP/Compaq ProBook 4530s