The Sido battery measures at about 950 mAh compared to 1500 mAh for the Nokia version so should give about 60% of the run time for about 35% of the cost (2.7 UKP or 5 US$) of the cheapest genuine Nokia BP-5L on Ebay (8UKP or 16US$ at the moment). I can find no reference anywhere on the internet to faulty Sido batterys or cells and think they are probably safe - as we would have someone telling us on here if they were not!