8000mAh Back-Up Battery with Screwdriver & Stylus Pen for 3DS (Actual 2000mAh)

Material: plastic housing
Capacity: 8000mAh (Actual 2000mAh)
Back-up battery for Nintendo 3DS
Includes screwdriver + stylus pen 

NDSi relevant product information

NDS vs. NDS lite vs. NDSi
The NDSi  has a brighter and more vibrant colors. Screen is also a little bigger.
In terms of size, there isn't much difference between the DS Lite and the DSi, but when you compare weight, the DSi is a considerable amount lighter than the Lite. For those of you who own a PS3, the difference is basically like the difference in holding a SixAxis and a Dual Shock 3. Speaking of controls, the DSi's D-Pad is considerably better than the Lite's.
The DSi now allows for downloadable software, includes 2 cameras for taking pictures, and allows for saving of voice recordings using the system's mic. All of the above can be saved to the DSi's internal memory or SD via the new port.
One of the biggest changes to the DSi is the inclusion of two low res cameras. These cameras have provided for quite a bit of confusion since the system was announced, so let us clear the air.
1. Both cameras are low res.
2. They are low res so they can easily be used in applications.
3. There is no flash on either camera, but there is compensation for darkness, much like any medium quality web cam. This also means that the video feed gets choppier and is more susceptible to blur in low light situations.