1" x 2" sodium iodide detector internally mounted, sensitivity: typically 700 CPM/Micro R/HR, meter dial 0-5 Micro-R/HR, multipliers: x1, x10, x100, x1000, alarm: a fixed alarm point can be set or a quick deviation alarm, built in unimorph speaker with on/off switch, uses two "D" cell batteries, weight 5 lbs.