This HP VH638AA compatible 4GB DDR3-1333MHz Dual Rank Unbuffered 1.5V 240-pin CL9 UDIMM is 100% guaranteed to be compatible with your system and to work right the first time. Adding additional memory is the best way to increase the performance of your system. All our memory is built to strict JEDEC standards to meet or exceed the Tier 1 OEM's factory requirements. Our products are also guaranteed by federal law to not affect or void OEM warranties.

• DIMM 4 GB memory allows you to have more programs open at a time
• 240-pin-pin DDR3 SDRAM operates at an effective bus speed with minimal power consumption and as a result, you get optimal computer performance with an improved memory heat dissipation
• Up to 1333 MHz speed for playing the latest games and using heavy software