AnandTech reviews the ZBOX CI662

 "The core thermal solution employed in the ZBOX CI662 nano is the huge heat-sink that completely envelopes the board except for the underside (to allow installation of a 2.5" drive and the DDR4 SODIMMs). Unlike other passively-cooled PCs, it is not possible to directly touch the heat-sink by accident. The heat in the fins are drawn out by convection through the plastic chassis with plenty of perforations in a honeycomb pattern. The plastic casing itself doesn't get very hot. The case also has either a flat profile or rounded edges around the spots where it is usually held to access the I/O ports or power button.

It is possible to build a passively cooled version of a Frost Canyon NUC with an after-market chassis for around the same or slightly higher cost - but the efforts needed to assemble the passively-cooled case may be too time-consuming for many customers. Pre-built passively-cooled NUCs also carry a significant premium. An almost ready-to-use mini-PC like the ZBOX CI662 nano fits this target market perfectly. Relatively speaking, $550 is an affordable price tag for such a system."

Source: AnandTech