Octal, is also a type of vacuum tube that uses a metal or more commonly a bakelite base with a large keyed pin in the base, and usually 8 pins arranged in a circular arrangement around the locating pin. The Octal was developed in the early 1930s to provide a more positive way to align the pins into the proper location in the socket than the earlier pre-octal tubes. Octal tubes usually had glass envelopes, but metal octals were developed during the late 1930s to provide built in shielding and mechanical strength. Metal Octals were popular in commercial equipment, communications receivers, and automobile radios because of their resistance to breakage and their built-in shielding. Another variation of the Octal tube, known as the Locktal or Loctal was developed, which became a popular alternative to the Octal due to its positive locking base.

Octals were joined in the 1940s and 1950s by the miniature tube. Miniatures were smaller and used less power than Octals, but they were unsuitable for many applications, such as high voltage rectifier tubes, high power audio and transmitting tubes, such as the 6L6 and 6146, and the Horizontal output and Damper tubes in Television receivers.

While transistors and integrated circuits have all but taken over most electronic functions formerly done by vacuum tubes, there are still quite a few Octals in service, mostly in radio transmitting equipment, guitar amplifiers, and tube audio gear.