A tube bait is a hollowed-out, cylindrical soft plastic lure with a tentacle-encased open end and a closed rounded head. Their purpose as a lure is to entice the bass as a real fish would. In the water, these tentacle-like segments float and move in a way that attracts bass.
They are usually made out of plastic or rubber (as being hollow is a key component). This adds to the lure mimicking the natural movement of a fish, helping slow its descent due to the air trapped inside as it begins to sink in the water.