The Foba RODUA Combitube Adapter is used as a light fixture adapter in the Foba Combitube System. This adapter comes with a male Combitube connector at its bottom and a 3/8" thread at its topThe Foba RODUA Combitube Adapter has an overall length of 3.1"Outer Top Diameter: 5/8"Outer Bottom Diameter: 1"Weight:0.13 lbs