Full Details from Amazon.com : http://www.amazon.com/gp/product/B005HIWD9Q?tag=onigi-20
Komputerbay 4GB DDR2 PC2-6400F 800MHz ECC Fully Buffered FB-DIMM (240 PIN) 4 GB w/ Heatspreaders
ECC Fully Buffered an FBDIMM will not fit into a standard DDR2 socket and a DDR2 module will not fit into an FBDIMM socket
Capacity 4GB For Apple Mac Pro 8-core Desktop
Speed PC2-6400F 800MHz
240-Pin DIMM
Lifetime Warranty