This is a butterfly valve for 1" ID pipes. It has a diameter of 0.986" so it should fit into most 1" ID steel and aluminum pipes/tubes. Two of these can be used for a DUAL Butterfly Valve, and can be linked with our joint lever and valve arm. Best get one made of Strong and flexible material. It can handle up to 80*C or in Alumide which can handle 172*C, but is a bit brittle. It has a flap on one side, to prevent overturning, and two small holes to allow for engine idle with the valve closed, without having to adjust the idle externally. Has a hole for 1/8" shaft. Use your own or our Shaft 0125 for 1" pipes. Don't get this in glass, since that shrinks by almost 10% in diam.