Equips with the newly developed photo diode and the microprocessor to measure gamma rays up to 9.99uSv/h (gamma rays only). Measuring range: 0.05~9.99uSv/h. error: 20%. Initial reading takes 35 seconds, thereafter updates result every 10 seconds. Feature: beep sounds on/off, battery indicator, auto-off. Dimension: 170mm (L), 22mm (D). Weight: 60g. Made in Japan. Uses one 1 AA alkaline battery for 60 hours of contentious use (note: a starter batter comes in the box only lasts for several hours). Factory calibrated with Cs-137. Unlike a typical Geiger counter using a GM tube, it never requires calibration again.