Polish Made Geiger Mueller Tube type DOB-80 was designed in Germany for production in Poland for their military Geiger Counters. Specs: 70mm (L) × 11mm (dia.). Recommended anode resistor 5 megohms, starting voltage 400V, recommended operating voltage 550V. Sensitivity to Gamma, Beta, and X-rays. Cathode material: stainless steel. Anode material: tungsten. Construction: glass envelope. Background radiation here in Scottsdale is about 9CPM. Retails for $45 and up. Each tube is tested before we ship.