2.5V 1.0F supercapacitor, also known as the notorious "Xbox Clock Capacitor". This capacitor stores enough charge to keep the Xbox clock from resetting while it is unplugged for a short time - similar to a battery.
The stock clock capacitor in the original Xbox (revisions 1.0 - 1.5) are often referred to as a "ticking time bomb" due to their poor quality. It is recommended that it be replaced before it leaks/degrades/corrodes/bursts and causes permanent damage to your Xbox. Xbox revisions 1.6 and will not need this replacement part.
This replacement clock capacitor is a high quality Easton branded part and is the recommended replacement. This listing is for a single capacitor.
Use our guide on identifying Xbox revisions to see if your console is affected by the faulty clock capacitor: Identifying Revision Number of Original Xbox