Original YUNEEC Q500 LiPo battery, which is well constructed and fit perfectly.

Features:
Suit for YUNEEC Q500 RC quadcopter
Rechargeable lithium polymer battery
Sustaining and high rate discharge, durable
Stable output current, protect your RC quadcopter
Specifications:
Brand: YUNEEC
Battery type: Lithium polymer
Capacity: 5400mAh
Cells: 3S
Voltage: 11.1V
Watt hour: 59.9Wh
Item size: 175 * 50 * 32mm
Item weight: 425g