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 unit 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 unit that has been modified with an IPS screen. (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 this product. 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. Since this product is made with a 3D printer, there may be slight variations, and it may be difficult to attach to the WonderSwan main unit depending on the individual unit. This listing is for the battery box only. Gum batteries and the WonderSwan main unit are not included.