The Rexroth A4FO is a robust axial‑piston fixed displacement pump employing a swashplate design — engineered for open‑circuit hydraulic drives in both mobile and stationary systems. Flow output is directly proportional to drive shaft speed and the pump’s displacement. The A4FO series offers high power density, impressive volumetric efficiency, and a compact footprint, making it suitable for heavy‑duty applications such as construction equipment, industrial presses, and marine hydraulics.