These true Joyetech batteries are universal and fit all eGo and 510 products. 

3.3v Rechargeable battery with 650mAh capacity will last a long time between charges. 

These batteries have a safety switch that will de-activate the button so that the battery can be stored without accidently being activated. Simply press the battery button 5 times and the battery will be de-activated. Press 5 more times to re-activate it for normal operation.

These batteries are the same as the Joyetech eGo/eGo-T batteries with a few added features as noted below.

New Features on eGo-C batteries include:

• Button LED changes color when only 25% battery life left
• Strengthened short circuit and over discarge protection
• Circuitry to prevent overcharging

eGo Battery is not compatible with 510 Charger.  Charger output must be DC 4.2V  420mA