As a lab teaching assistant for first year undergraduate students in engineering, I occasionally get really interesting questions. In fact, I was asked a really good question during an electrical circuits lab a few weeks ago. The lab itself was pretty easy. Students just needed to build a bunch of simple circuits using only resistors. A guy came to me and asked, "Can you explain to me how a digital watch’s circuit works?" I found it was extremely hard to answer this question, despite how simple a digital watch’s circuit was to me. The reason was I did not think the student had enough knowledge to understand something of this level. A simple device, say a digital watch, has resistors, capacitors, transistors, crystal, diodes, operational amplifiers, and other electronic components of this nature. Therefore, I just told him to think about this question after the end of this term. At least by that time, he can have a better knowledge of electronic components. Fortunately, to review a CPU cooler, we do not need to know much in thermodynamics. There are some simple and straightforward criteria I use for evaluation. More specifically, my criteria includes the overall design of the cooler, installation experience, and of course, its cooling performance. Is today’s review unit, the Scythe Mugen 5, a good CPU cooler for these criteria? Let us find out.