The battery fit and work for my Nintendo DS, but it is certainly not a 2000 mAh. An original Nintendo Battery is 1000 mAh and last about 10h. This one lasts around 2h to 3h after a full recharge. So it is probably more a 200mAh~300mAh. Which suits me considering that after years of use, the original battery only lasted 5 minutes. But why be dishonest about the specs of the merchandise? In the long run, it does you no favours. Or is it perhaps an aging stock? Also, I would have paid the same price (if not more) for 1x 600mAh, rather than 2x300mAh, but whatever.
Replacement battery indeed, but doubting the mAh...