Vacuum tube skulls

Noah Scalin's bonus skulls on his skull-a-day site, made from two- and three-inch vacuum tubes, are tremendous: "Most of the ones I own have this extra bump at the top so I decided to try leaving it unpainted giving you a peek inside and making them have a bit of an alien/robot feel."

[BONUS] 399/400. Skull Tubes Mach-2 I & II