Fluid power scientists and engineers have produced a large amount of high quality books so far, which cover a vast amount of technologies involved in this field. Names like H. Merritt, D. McCloy, H.R. Martin, W. Backe, J Watton, K. Edge, M. Ivantysynova, N.D. Manring among many others must be considered as the milestones in this field; their scientific publications and books have inspired generations of engineers. The first author of this book was lucky to be able to closely work for over 10 years with Professor John Watton, and in fact, most of the original research presented in this volume was undertaken at Cardiff University. The present book focuses on several components of fluid mechanics. The first three chapters are designed to give a proper background to the reader regarding the main fluid characteristics, chapter 1, the main fluid mechanics equations, chapter 2, and a strategic background of the Computer Fluid Dynamics (CFD) techniques, chapter 3. It must be kept in mind that nowadays, conventional mechanics, as well as fluid mechanics, are fully immersed in the CFD era, therefore the components design desperately needs the use of this relatively new tool. Chapter 4 introduces original research based on fluid mechanics understanding of relief valves and servovalves, dynamic and stability considerations are being given in both cases, and hints to solve stability problems are provided. Chapter 5 also provides original research on, very likely, the most complex machines in the fluid power field; piston pumps and motors. In fact, chapter 5 focuses on axial piston pumps, although the information gathered in this chapter can be directly extrapolated to other piston pumps and motor configurations. In Chapter 5 the reader will find a thorough mathematical description of how slippers with non vented grooves can be designed, the effect of grooves on pistons is also thoroughly analyzed. The barrel dynamic movements and piston pump pressure dynamics under different operating conditions are also introduced in this chapter. In all cases, the reader will be able to extract ideas of how a proper design shall be obtained. It is important o highlight that all experiments presented in chapter 5 were done by the book’s first author in the Professor John Watton Fluid Power laboratory at Cardiff University UK, this is why Professor John Watton has to be seen as a co-author of this particular chapter. Chapters 6, 7 and 8 are designed to introduce some details which are often forgotten in many publications; these are the use of accumulators, the importance of proper filtration and the use of cartridge valves whenever fluid pressure and flow are overcoming a certain value. It is crucial to realize that accumulators can vastly improve a given circuit efficiency, often saving large amounts of energy. A proper filtration is crucial to increase the components life and prevent system failures. According to the authors’ understanding, the present book may very well be used as a design tool for several Fluid Power components. Manufacturers, Engineers and fluid Power Researchers may get some helpful ideas to improve their products