Our largest and most sensitive geiger counter kit uses a Russian Geiger Mueller tube. This tube is 0.75” in diameter x 7.2” long and because of its large surface area it is so senstive to beta and gamma rays that the background count here in Arizona on this kit is about 100 counts per minute. Operates on one 9V battery (not included). Flashes a bright red LED and “clicks” from a small on board speaker with each particle detection. Size of PC board is 7-13/16” x 1-7/16”. Complete with all parts, GM tube, and instructions. Requires soldering. No case available.