The left side of the Duet (or bottom, depending on which way you position it) has a grill opening in the front corner. Immediately behind the vent is a fan bracket sized for a standard 80mm fan which is not included. Although not apparent yet, (we'll take a look inside next) this is the exhaust port for the power supply and you will definitely want a fan to put in this location. Also if you lay the case down flat the vent is blocked so the case will need to be raised up off the surface. The rear of the case holds two 80mm fans which are included, directly above the I/O motherboard plate. I was surprised NZXT was able to squeeze them in there, most desktop cases I've seen use at most a 60mm fan in this position. One riser slot has a removable plate cover, the rest are snap-out pieces. The last riser on the far right holds a standard power cord receptacle which may seem a bit strange until you realize there's no opening for a power supply here.