OCZ OCZ3N1800SR4GK DDR3 1800MHz 4 GB Kit NVIDIA SLI-Ready 1800MHz DDR3*/Unbuffered 8-8-8-27/CAS-TRCD-TRP-TRAS) 1.9 Volts/240 Pin DIMM Available in 1GB and 2GB Modules Available in 2GB and 4GB Dual Channel Kits/ OCZ Lifetime Warranty