The VA-Z-115 Geiger Mueller Tube is very sensitive to beta and gamma ray detection. It requires about 450VDC for operation and works great with our C8600ASB - Assembled Geiger Counter Board (not included). This tube is new and tested. It was made in East Germany during the Cold War. Size of tube is about 3.23" long x 0.55" dia. (base metal flange is about 0.83" dia.) The background radiation count here in Arizona is about 35 counts per minute. Center pin is (+) and metal base is (-).