The II Quaternary Pump is a gradient pump that uses low-pressure mixing for UHPLC gradient formation and solvent blending from up to four solvents. This pump operates at pressures up to 600 bar and flow rates up to 10 mL/min. The II Quaternary Pump combines proven reliability with highest flexibility in automated gradient formation and solvent blending, and is recommended for a wide range of research and routine applications as well as for method development.