Note: It is some sort of water- resistant, not waterproof. Please do not sink it to the water. For the most of the buyers, One of the most annoying things about these stopwatches is the random beeping. Please read our product manual. If you still do not know how to stop the beeping , just send us an email via and we will offer you efficient and professional help. 1 Small Screwdriver - When the original battery is almost exhausted, you need to remove 6 tiny screws to replace the battery. It is not easy to find a suitable screwdriver when you need it. Good news. You will get 1 pcs if you make a order from our shop. Lightweight and Portable - The Stopwatch is made of hard plastic and is light weight. Each stopwatch comes with a 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. Precice Stopwatch and Spare Button Cell - Measure time at an accuracy of one hundredth of a second. Use the split time feature to precisely measure multiple events. Only powered by 1 AG13, and we offer 1 spare AG13 for each stopwach. Very Easy to Operate - The Digital Stopwatch is very simple to operate with 3 keys : 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 70 dB). Suitable for running, swimming, training, tracking match, competition, athletics, etc.