Durable design: Stainless steel body, molded rubber shell. Silicone gel filling and epoxy resin protect the internal electronics against shocks. Completely waterproof: Sealed against liquids, works under water. Automatic card reading: Detects and reads signal cards without button pressing, making the unit easy to use. Specifications: Memory Capacity: 28,671 records Energy usage during stand-by: 0.06mA Battery Life: over one year with a single battery average 200 readings per day Reading distance: 5cm to 10cm PC Connections: wireless connection Operating Temperature: -20C to 70 Operating Humidity: 0% to 95% Size: 120 x 35 x 26mm Weight: 200g Battery: 3.6V lithium battery CR123A