This Nintendo 3DS XL Circle Pad Pro provides the user with an additional analogue stick, for games where you need to move the character and camera together. When attached, the 3DS XL looks rather frankenstein-esque, however, this accessory add-on is comfortable to use and the analogue stick provides good movement and is smooth. When attached to the console, the circle pad pro still gives you access to volume controls, the ability to charge the 3DS XL and access the headphone jack.
Do note that not all games work with the Circle Pad Pro. I have been using it with 'Metal Gear Solid Snake Eater 3D', and the game is far easier to play using the additional analogue stick, than having to use the 'Y, 'X', 'A' and 'B' buttons previously. The Circle Pad Pro uses one AAA size battery and one is supplied in the box. Highly recommended for players who want a more comfortable control method, when playing games on the 3DS XL.