Having bought four of these units for judging freediving competitions I was looking forward to using them. Firstly one of the units was not quite as waterproof as the manufacturers claimed they were, but after returning the unit to the UK, another unit was sent to replace the faulty unit. Three months later when the next freediving competition came along, got the four units out and three of the units had flat batteries. Managed to fix two of the units, but since you have to undo six poor quality screws to get into the unit, I am now two screws short of being able to fix the third unit, due to the screw heads rounding off. I also had to fix the front button, which sticks (and to be honest probabaly caused the battery to run out). I would not recommend these stopwatches unless you only want to use the units once.