This 24V 8Ah Li-Ion "easy swap" battery pack is compatible with the X-Treme XB-200Li, X-Treme XB-210Li and X-Treme City Express folding electric bicycles. The battery can be easily removed and charged externally or charged while attached to the bike. Having an extra battery pack with you when you ride is a great idea. It doubles your range! This battery comes with a one year manufacturer's warranty.