Based on Noctua"s compact NH-U9 series and fitted with the award-winning NF-B9 fan and NT-H1 thermal compound, the NH-U9DO forms a complete premium quality package that provides excellent quiet cooling performance for 4U Opteron workstations and servers. The NH-U9DO"s SecuFirmTM mounting system is fully compatible with the standard backplate and makes the NH-U9DO a simple drop-in replacement for AMD stock coolers.