First off, you'll want one of these: Acekard2i - Another wonderful cart with the incredible AKAIO firmware. A must have for any DSi owner who doesn't care about GBA emulation. Compatible with all DS models and the 3DS. R4i Gold 3DS - Don't be fooled by the R4 name. This is a wonderful cart for both the 3DS and DSi, as well as the DSlite or DS Phat. No matter what you have, this will work for you. It runs the fantastic Wood kernel, giving it top notch game compatibility. For the price, it's hard to beat. Note: The page I link to is for the correct R4i Gold cart. Beware of imitators. Only the product from the following site is legitimate: http://www.r4ids.cn/ Compatible with all DS models and the 3DS. OR R4 Original - 2GB capacity is the main limitation of this cart. Otherwise it has compatibility on par with the top carts with the addition of Wood R4. (If this costs more than $4 or $5, it isn't the R4 Original - It should specifically note that there is 2GB max, non-SDHC.) As Loony mentioned, you will need a MicroSD card no matter what, and the kernel is entirely drag and drop for every cart. Nothing you buy will be directly insert and work. It will always require some work on your end.