The CNPS6500 comes in a couple of flavors. There are two variations with heatsink material—the aluminum copper hybrid or the pure copper. Then there are two variations in mounting system—through the motherboard holes via screws or with the use of the socket 478 heatsink bracket that comes with all motherboards. We were fortunate enough to receive the CNPS6500A-Cu. The “A” denotes the mounting system, which in this case, was mounted through the motherboard holes. The “B” would mean that the heatsink mounts through the use of the socket 478 heatsink bracket. The “Cu” denotes that the heatsink is all copper while the “AlCu” denotes the aluminum copper hybrid.