The Potter VSR is a vane type waterflow switch with non-corrosive insert for use on wet sprinkler systems. It is UL Listed and FM Approved for use on steel pipe. Models available for pipe sizes 2″ through 10″. The Potter VSR series is the industry standard for flow switches for fire sprinkler systems and is compatible with the widest range of pipe schedules (5 through 40) in the industry as well as all necessary listings and approvals for installation worldwide.