The first two called for a single tube containing two levels of traffic.

He went down the narrow corridor, lit by a single tube of fluorescent light.

If a single tube could not be built with the required performance, an obvious solution is to use multiple tubes, one for each color.

A single tube can grow up to 5 feet high and 3 inches thick.

The six barrels were housed together in a single rotating tube.

The tunnel consists of a single tube, with two traffic lanes.

The tower was hollow, just a single tube of stone.

Its tip was not a single tube as Slade had expected.

Guests can ride in a single or double tube.