HD1 series variable piston pumps for closed loop are axial piston pumps with swash plate design and optional drive shaft. These pumps are specifically designed for closed-circuit hydrostatic transmission. Throughput is proportional to speed and swash plate Angle. When the inclination Angle of the swash plate increases from 0 to a large position, the throughput increases. Reverse the Angle of the swash plate and the flow is reversed. The technology selection allows the new unit to operate at pressures of up to 400 bar [5800 psi].