The Model 521 is a high performance, compact solvent delivery module that has been designed to compete with the most expensive pump systems on the market in reliability and performance without the high cost. A dual piston design with solvent compressibility feedback assures virtually pulse-free and accurate solvent delivery. The Model 521 has all of the features of the Model 520, but without gradient programming capability. It may be used as an economical stand alone pump for isocratic operation, or in conjunction with a Model 520 for gradient operation. UHPLC (Maximum pressure: 15,000 PSI) is available for Analytical flow. Also Titanium pump heads and Biocompatible PEEK pump heads are available for all flow ranges. PEEK pump heads are not listed below, please contact us for ASI part numbers. Dual primary pump heads are also available, please contact us.