This is a battery box that allows you to use gum batteries with the WonderSwan, WonderSwan Color, and SwanCrystal. Compared to using dry cell batteries, the main body becomes flatter and easier to hold. This is especially effective when using vertically-oriented software. Battery life is approximately 3 to 2.5 hours with a WonderSwan Color main body that has been IPS-modded (varies depending on battery condition and other factors). Important Notes: In addition to this product, you will need gum batteries and a charger for gum batteries to use it. Do not use the WonderSwan's dedicated charger. Charging the gum batteries while they are in the battery box may cause the battery box to deform due to heat generated during charging. Because it is 3D printed, there may be slight variations, and it may be difficult to attach to the WonderSwan main body depending on the individual unit. This listing is for the battery box only. Gum batteries and the WonderSwan main body are not included.