This is an Intel Active/1U Combo Aluminum Heatsink for the Dual-Core and Quad-Core Intel Xeon processor 5100, 5200, 5300 and 5400 series.
Compatible Intel XEON CPUs are:
XEON DP Dual Core E5205
XEON DP Quad Core E5345
XEON DP Quad Core E5405
XEON DP Quad Core E5410
XEON DP Quad Core E5420
XEON DP Quad Core E5430
XEON DP Quad Core E5440
XEON DP Quad Core E5450