Heatsink Top:
The fan clips into a plastic fan shroud which reduces the overall size from 80mm to just 70mm. This allows the larger fan to be attached to the smaller width heatsink. Inside the cone-shaped fan shroud are a series of blades whose purpose it is to constrain and direct the airflow from the larger 80mm fan evenly. Since the fan shroud clips into both the heatsink and fan, no screws are required.

Side A:
This is a tall heatsink, and given that it measures 98mm high, may not fit in certain small form factor computer chassis. From this side we get a better perspective concerning how this heatsink is actually built. The base is 7mm thick and the fins 1mm. Fins are spaced ~2mm apart and measure 37mm long. The clips which lock into the P4's HSRM are screwed into the copper base, and are pretty easy to operate.

Side B:
The clip mechanism which is used to lock onto the HSRM is simple and pretty effective. Each corner has a small tab which locks into the plastic tab to hold the ACP4LC firmly in place. Here again we can see just how thick the copper base is.

The copper base measures 83x69mmn size, and is 7mm thick. The copper is soldered in place so the thermal interface should be pretty decent. The base has a milled finish which is pretty smooth, and quite flat. The heatsink comes with a small aluminum/graphite thermal interface pad pre-installed.