This clock has a bad design. When I bought it I thought it would be a direct replacement for my old little Casio stopwatch, but it's not. All watches are larger and chunkier, which in itself is not an obstacle. The real problem is that the function keys don't work reliably. First, they are buried between protruding ridges, so you have to gently press on them with your fingertip at a certain angle or with a stylus. Even then, they only work about 30% of the time. The stopwatch needs to work reliably as soon as the button is pushed, and when someone is running intervals or other workouts, there's no time to stop and check the button to push it in exactly the right direction, and even then it's going to fail more than half the time. On my old watch, the buttons worked 100% of the time no matter how they were pressed. My score for "timer function" would be zero, but that's not an option. I advise against buying this watch.