| Acorn. Miniature glass envelope with side contacts. About the size of an acorn |
| Balloon envelope shape. Glass sphere or rounded top. |
| Classic envelope shape. Glass tube with rounded top and centre bulge. |
| Thin Glass Tube. Tubular glass envelope less than 25 mm diameter. Used for miniature valves. |
| Thin Metal Tube. Tubular metal envelope of 25 mm diameter or less. The shape of rugged WW2 American valves. |
| Wide Glass Tube. Tubular glass envelope of greater than 25 mm diameter. |
| Wide Metal Tube. Tubular metal envelope of greater than 25 mm diameter. |
| Side Window. Any glass envelope with a viewing window in the side. Mainly tuning indicators. |
| End Window. Any glass envelope with a viewing screen at one end. Typical Cathode Ray Tube design. |
| Co-axial. Appears as a cone with cylindrical contact rings. Used for high frequency power valves. |
| Pinch. The original construction method. The electrodes are held in a fishtail of glass. The wires connecting to the base pins pass through the length of the pinch. |
| Glass Disc. The electrodes are fixed into a sandwich of different glass types. The supports and base pin wires pass through a short glass path. |
| All Glass. The glass disc base has the contact pins directly moulded into it. No separate base is required. |
| Disc Seal (Glass). The conical structure is built using glass ring insulators bonded to the metal ring contacts. |
| Disc Seal (Ceramic). The conical structure uses ceramic rings as insulators. And is capable of higher operating temperatures than glass. |
