Mainly used for learning and experiencing the high-speed data processing ability of single-chip microcmputer and measuring the flight speed of various things. Features: This product is mainly used for object acceleration and velocity measurement. Individual users can be used to measure the design speed of all kinds of shoot playthings. Mini size is easy to carry. Simple and easy operation. Handheld type speed measuring instrument, with high accuracy measurement, 160 groups datas will be recording. Measuring speed ranges: 1-999m/s. Metal surface and fully closed, this speed measuring instrument will not affect by thesun and air current. High accuracy, with accurate measurement data. Humanized design unit conversion function. How to Use: LCD backlight setting, you can set constant light or long out. When you set as automatic, the screen will light out after 10 seconds without operation. With automatic shutdown function. Charged by USB line, about 1 hour chargetime then you can use more than 10 hours after fully charged. The red light bright whilecharging and the blue light bright in fully charged. Built-in overshoot protections, overdischarge protections, short-circuit protections, etc. With holders and pinboard package. Without using the pinboard, the using pipes diameter ranges is 20-31mm, less than 20mm you can add the pinboard or tie on the pipes. Using the pinboard, the using pipes diameter ranges is 16-43mm, less than 16mm you can add the pinboard or tie on the pipes. Included three buttons, first is switch button also is confirmation button, second is up button, third is down button. With Chinese and English switching function. You can change the language by yourself, press the down switch after starting up, and find the language line and press the confirmation key. Using semipermeable half-reflecting LCD screen that you can see clearly in the darkness or in strong light. Specifications: Working Voltage: 5V Measuring Pipes Caliber: 10mm Accuracy: test error less than or equal to 0.5% Measuring Speed Ranges: 1-999m/s Cell(built-in): 1 * 5V 300mAh Lithium Cell Item Size: 73 * 44 * 33mm / 2.9 * 1.7 * 1.3in Package Size: 100 * 60 * 50mm / 3.9 * 2.4 * 2.0in Item Weight: 85g / 3.0ounce Package Weight: 174g / 6.1ounce Notes: Please allow 1-30mm error due to manual measurement. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Packing List: 1 * Speed Measuring Instrument