As low second battery I chose this product. I had already done with another battery that company for another camera good experience, so I did not hesitate for our new underwater camera again access at vhbw. The battery also worked properly and could be used perfectly in the Nikon S31. However, he could only be extremely tedious remove it again. When you press the unlocking via the battery compartment, the battery would actually jump out a bit, but he did not. It helped only (straightened) Sample bag staples that we put into the space between the battery and tray and simultaneous knock on the table to carry the battery pack as far from the tray that you could touch it and then pull it out. He does not strike me again in the camera, because I'm afraid to damage the professional and / or it eventually no longer elicit. Thus, the battery seems to be minimal thicker than the original and can at least my camera model probably get over not. Therefore, I have asked for reversal of the seller, which worked perfectly well, fast and friendly. Conclusion: For the S31, I would not recommend this battery therefore, with other models of the size difference may possibly not be so serious.