This Cisco ASA5520-MEM-2GB compatible 2GB (2x1GB) Unbuffered factory original 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 memory is built to strict JEDEC standards to meet or exceed the Tier 1 OEM's factory requirements. The products are also guaranteed by federal law to not affect or void OEM warranties.