This 4GB DDR2 SDRAM memory kit from G.SKILL includes four 2GB modules, each with a bus speed of PC2-6400 (DDR2-800). The memory features include unregistered, non-ECC, and unbuffered profile, with a standard form factor of DIMM. The memory voltage ranges from 1.8V to 1.9V, and the kit model number is F2-6400CL5D-4GBPQ with 240 pins. This memory kit is compatible with desktop computers and has no California Prop 65 Warning.