Their description:
Product Description
Recharge your Xbox 360 Wireless Controller while you play and kiss disposable batteries goodbye! Complete with a charging cable and rechargeable battery pack, the Xbox 360 Play and Charge Kit is all you need to juice up your Wireless Controller - even in the midst of battle…. More >>
Go & get it here - i can recommend it:
Xbox 360 Play & Charge Kit
Do not purches this, its a good theary and all but your jist makeing a wireless controler wired and giveing your self a bigger pain to deal with. Purches the Quick Charge Kit, it comes with the rechargibal battery and is way less of a hassel.
if you want to be truely wireless then dont buy this. you have to plug it into a usb port or your xbox 360 to charge which means you have to be wired to charge. better off getting batteries or rechargable batteries.