Each Consists of 2 Tight-Fitting, Tapered Connectors. Full range of sizes to fit tubing from 3 to 12mm (1/8″” to 1/2″”) I.D. Consists of two serrated polyethylene connectors which assemble tightly together with a male-female center taper. Very useful in connecting and disconnecting vacuum lines and other tubing assemblies. Use on filtering flasks to avoid accidents. All sizes are interchangeable to make reducing combinations. 12 per bag.