After removing the fan and the plastic fan shroud from the Eaglestream we are able to see the top of the copper insert in the center of the clip trough. Unlike some Thermaltake heatsinks which also come equipped with copper inserts, this copper core does not peak out above the base of the fins at all.

Leaving the recess for the copper core withing the aluminum should be beneficial for the overall heatspreading efficiency of the cooler. With the copper in direct contact to aluminum on essentially two sides, there is more direct contact for heat transfer to occur over.

From the best we can tell the copper insert is press fit into a hole milled from the heatsink extrusion. Technically termed an 'interference fit', there is generally a pretty good thermal interface between the two metals which are in very close contact.

The exceptions crop up if the materials are not properly toleranced before being joined, or if the aluminum has been anodized. Anodizing creates a crystalline coating on the aluminum which can interfere with the best possible thermal transfers.

Spire 5R266B1H3 Heatsink From All Angles
	The Fans: The small 10mm thick 60mm fan sits in this plastic fan shroud for reasons we really aren't to sure of. The fan grill is a nice addition, but with the RPM's hanging around 4800RPM it really isn't too necessary so it was nice to see Spire took the extra step and included it anyway.
	Bare Heatsink: With 6mm area cut from the center of the heatsink for the stainless steel clip, the Spire 5R266B1H3 is pretty standard as far as fin design goes. The fins are smooth, with no scalloping effects, and just two small cross cuts along the outer edges.
	Side A: Fanner, the parent company of Spire sent over the blueprints for this heatsink so we can tell you that the three tab clip is made from heat treated SUS301 stainless steel. The fulcrum is 27.9mm from the rear connector tab. The clip is entirely tool based so get out those flat head screw drivers.
	Side B: The 27 fins are all 32mm tall, 0.5mm thick and spaced 1.5mm apart, so this isn't a configuration we haven't seen countless times before. The base is 10mm thick which is thicker than what we typically see from extruded heatsinks.
	Heatsink Base: The base is machined flat, and after pulling out the straight edge we can see that things are as good as they look. The copper insert is 30mm in diameter and about 6mm thick. The heatsink comes with a gummy thermal interface pad which we removed to keep our tests consistent.