Armstrong S-35 BF In-Line Circulators are apart of the Series S. The 1/6 HP bronze fitted circulator pump is suitable for hydronic heating and cooling, domestic water systems, mulit-stage zoning and general industrial service applications. Built using a standard three-piece design that features a radially-split body, oversized shaft, centrifugal impeller, positive mechanical seal and modular construction, Armstrong Pumps Series S Circulators are a trusted, durable product that have been used by HVAC professionals for decades. Features: Standard three-piece design Radially-split body: Can be left in-line while servicing pump, eliminating disconnecting of pipes Oversized shaft: Made from special alloy steel Centrifugal impeller: Ensures maximum water delivery in the HVAC system Positive mechanical seal: ARMseal construction ensures many years of noise-free, trouble-free service Modular construction: Unique shaft and bearing module fits for ease of serviceability and reduced inventory costs