A vacuum tube is a bulb or tube that acts as a barrier to outside gases and contains a vacuum. Depending on the kind of tube, it can change or amplify electric currents that pass through it. Though less commonly used today, vacuum were used in everything from televisions and radios to amplifiers and hearing aids. And are GLASS and now are useless, So individuals like myself have found ways you UP_CYCLE them into Jewelry and many other things.