360° View - NZXT Respire T40 Heatsink Information on Frostytech's test methodology is available here.
NZXT's Respire T40 heatsink ships with a 120mm fan. Additional fan brackets are supplied to attach a second fan on the rear of the heatsink. Standing 158mm tall, it has four 8mm diameter copper heatpipes exposed at the base which make direct contact with the processor IHS. Each aluminum fin measures 0.4mm thick and is spaced 2.0mm from the next. The bottom-most fin is elevated 38mm above the base for motherboard clearance.
The four 8mm diameter copper heat pipes are set into a 12mm thick aluminum base plate and exposed at the base. The base pate provides support for the mounting brackets. Note the slight jog in each aluminum fin at the middle of the heatsink.
The exposed heatpipes on the base of the NZXT Respire T40 create a usable surface area of 38x40mm. Looking at the top of the heatsink, we see the heatpipes are spaced ~6mm from one another and 65mm across (in the highest airflow region).

Base Finish and Flatness

Flipping a heatsink over to inspect the business end is often a simple indicator of overall cooler quality. More practically speaking, a heatsink is in many ways only as effective as the contact it makes with the processor - the flatter and smoother the better. Base finish is one of the criteria that Frostytech measure in the course of evaluating heatsinks, and it involves two distinct aspects. Surface Finish is the first; this is calculated with the aid of Surface Roughness Comparator that has a cross section of common machine surface finishes and their numerical surface roughness equivalents in microinches. The second is Surface Flatness. This is tested with an engineer's straight edge or proven flat surface, in two axes.

The exposed heatpipe base of NZXT's Respire T40 heatsink has a sanded surface finish with a surface roughness of approximately ~64 microinches. The base is generally flat in both axes, but not perfectly so.

Up next, heatsink sound level comparisons....