Taco Universal Cast Iron Flo-Chek - 1 1/4" NptTaco Flo-Cheks are used in forced hot water heating systems to prevent "gravity" circulation during periods when the boiler is hot, but the space heating zone is not wanted. You can also use Flo-Cheks in systems with multiple circulator zones to allow heat to flow only into the zones that are calling for heat. Product Specifications: BRAND: TacoINLET CONNECTION NPT INCHES: 1-1/4" CIDESCRIPTION: FlocheckPACKAGE QUANTITY: 1MANUFACTURER'S PART NUMBER: 221-6