Note: It is some sort of water- resistant, not waterproof. Please don¡¯t sink it to the water. The beep is very quiet that you'd notice it in quiet environments. Each stopwatch comes with a button cell in its compartment and 1 spare button outside. You have no worry about its battery power. 1 Small Screwdriver - For most stopwatches on the market, when the battery is almost exhausted, you need to lift the back cover to replace the battery. Sometimes it is not easy to find a suitable screwdriver when you need it. Good news. You will get 1 pcs when you choose to make a order from us. Only powered by 1 AG13 button cell. Note: please keep the small screwdriver and spare button cells from your kids for safety. Lightweight and Easy to Carry - The Stopwatch is made of hard plastic and is extremely light weight. Each stopwatch comes with about 40" black lanyard that is tied at the end. You can take it with 1 hand , put it in your pocket , or Stowed around the neck with the lanyard. Very Easy to Operate - The Digital Stopwatch is very simple to operate with 3 keys to control: Reset, Start/Stop and Mode. It has 1 group of count up function (1/100 sec, Maximum : 23 Hour 59 Min 59 Sec ), time(12/24), calendar, week and 1 group of daily alarm (About 65 dB). Suitable for running, swimming, training, tracking match, competition, athletics, etc. Real Simple Stopwatch - Some customers told us that they suffer products that have too many unusable features, unintelligible instructions, and require complicated procedures for achieving simple functions, yet fail to perform the most basic of tasks. So we listened and have removed some unnecessary functions.