FOR SALE: 866AX Mercury vapor rectifier... New AMPEREX 866AX Tube "Made In Holland" New old stock, excellent condx and in original box. Most places sell these USED for around $25.00 to $30.00 QTY 1 available for $8.00 plus shipping. https://www.tubeworld.com/866a.htm http://www.vacuumtubes.com/price9.html