This is a GE 6386 vacuum tube (one piece), used in legendary Vari-Mu compressors such as the early Fairchild 660/670 and MANLEY Gates. Only heater continuity has been confirmed for this listing. It is old, so the box is damaged and has been repaired. Sold as-is. These tubes are extremely difficult to obtain worldwide and are rarely available, resulting in high prices. One has been sold, so there are three left. First come, first served.