The Rechargeable Battery Pack for the Xbox 360 controller contains two AA nickel metal hydride (NiMH) batteries inside a sealed casing, with a custom connector on the rear to allow charging through the Xbox 360 controller itself. The pack provides up to 25 hours of continuous gaming for the wireless controller. It is recommended in place of disposable AA batteries, due to the replacement cost (in both economic and environmental terms). It also ships as part of both the Play & Charge Kit and Quick Charge Kit. An upgraded version of the "Rechargeable Battery Pack", which provides up to 35 hours of gameplay, is included with "transforming d-pad" wireless controllers.