The desirable triple attributes of high energy efficiency, power density, and dynamibility in fluid power transmission systems are simultaneously achieved with axial-piston type pumps and motors in which the displacement volume could be varied in a wide-enough range. A brief survey of hydraulic pumps and motors, as well as of circuits combining both, which satisfy this requirement to a more or less sufficient extent is presented. An innovative design of an axial-piston, bent-axis unit that should excel in fulfilling this requirement by being able to tilt the cylinder block up to a larger angle without compromising the durability of its synchronization components is presented in detail. This unit differs in several design particulars from conventional, commercially available ones. It features appreciably higher values for the power density and for a figure of merit—herein introduced—which is obtained as the maximum displacement volume divided by the total piston area.