Acorn tube
![The 955 is typical of the acorn designs, named for the glass cap holding the terminals with the main part of the tube extending from it.](/Images/godic/202412/19/955ACORN1353.jpg")
An acorn tube, or acorn valve, refers to any member of a family of VHF/UHF vacuum tubes starting just before World War II. They were named after their resemblance to the acorn, specifically due to the glass cap at one end of the tube that looked similar to the cap on an acorn. The acorn tubes found widespread use in radios and radar systems.