Usage Tips: Twist One Button Operation DSo simple that elderly grandma and 5-year-old kids can use it easily.Siliver knob and Black body,just twist the knob to set the time,press to start or stop .The digital light will be darken in 5 seconds and shutdown inanother 5 seconds,which can last battery life. With magent on the back , you can stick to classroom whiteboard , cooker,task, students tablet, iron wall, fridge, sports gym or other steel place. help students focus on study , Time Management on shower ,games etc , teacher organization for classroom,mothers cooking ,baking ,egg boiling 3 inch Large screen with Constant Bright Function. The Constant Bright digits make it easy to read at a long distance.Even in big meeting room, classroom ,or big kitchen, exercise room. 3 levels alarm sound mode,can be silence ,normal,or up to 90db. Does not beep unnecessarily when making a timer setting. Can hear this alarm in another room,no more worry about overcook.Blink led digital number will remind you when time arrival in Silentmode. Specifications: Material: Electroplate knob +ABS Volume gears:Mute 0db/normal 60-70db/Loud gear 80-90db Voltage: 4.5V Size: Diameter 3 INCH * 1 INCH Installation:for Hanging or standing Operating temperature:0-50 degree Timing range:0-99mins 55secs Power batteries:3*AAA 1.5V batteries (not included)