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Since Brown [1] built the first magnetic refrigerator prototype working near room temperature in 1976 there has been a large number of different prototypes [2] designed and built over the past 40 years. However, despite there being 4 decades of scientific input into the field of magnetocaloric energy conversion near room temperature, the technology is only now at the brink of commercialization. With every new prototype that is built, we see slow but measureable improvements toward the desired goal. Figure 7.1 shows the number of prototypes built until 2014. It is clear that the number of prototypes increases with each new year, pointing to the fact that the magnetocaloric energy conversion research community is expanding research activities together with the S-curve of technology development.The reasons why magnetocaloric technology near room temperature is only now slowly becoming market-ready lie in the fact that there are a number of different obstacles regarding the device's design, which need to be overcome before finalizing the idea of commercializing magnetocaloric technology. Addressing all the design issues is, of course, a difficult task. With each prototype built researchers try to solve different design issues, ranging from the heat-transfer problems of the AMRs and the working fluids, the design issues of the AMRs and magnet assemblies, to the problems related to peripheral elements, such as pump and valves systems. In this manner, each prototype built up until now has its own special feature. Each of them is trying to address one or more of the engineering barriers, but almost never a system as a whole.However, there is one major characteristic that can be distinguished for all the existing prototypes. There are two groups of devices, i.e. the ones operating in a reciprocating (linear motion) manner and the others operating in a rotary manner. The reciprocating and rotary operations of the magnetocaloric device are more or less related to the way how the AMR is exposed to the alternating magnetic field, as is described in Chap. 4 on Active Magnetic Regeneration (see also Chap. 8). One possibility is to move the AMR or the magnet in a reciprocal direction back and forth, and the other is to rotate the AMR or the magnet. As you will see in the following sections, each of the two methods has its pros and cons, depending on the functionality of the device. Is it an experimental testing device? Or is it a real