Grundfos 96453577 CR/CRI 5-4 Chamber Stack Kit. This Chamber Stack Kit is a genuine replacement part designed for CR/I Series Pumps and manufactured by Grundfos. This Grundfos 96453577 CR/CRI 5-4 Chamber Stack Kit features multiple cylinders and "Stacked" impellers individually designed to meet your pumps flow and pressure requirements. The Chamber Stack Kit mounts within the actual pump, and provides the ultimate in-line multi-stage pump performance. The Chamber Stack also features an exterior body and exterior parts constructed entirely of Stainless Steel.