A combination of a cap and tube in which a tube has an opening terminating in a tapered nozzle with an open end. The nozzle has a first diameter proximate said tube and is designed for rotational engagement with a cap. The nozzle includes a ring with a diameter which is the largest diameter of the nozzle and is located at least a band width distance from the junction of the nozzle to the tube. The cap is sized to engage the nozzle at its open end and has a closed outer terminal end. The outer end of the cap includes an axially centered locating cup for engagement with the outer open end of the nozzle. This forms a first seal in a first position and a second seal in a second position which is closer to the outer cap end by the band width distance. The cap is designed for rotational engagement with the nozzle. At its nozzle engaging end, the cap terminates with a circumferential band having an axial width defining the above mentioned band width distance. The band has a frangible junction with the cap to permit removal therefrom. It also has a flange positioned to fit over the nozzle ring to fasten the cap to the nozzle. The cap can only be removed or moved to the second position when the band has been removed.