The 
Nuprol Power 7.4v LiPo 1600mAh double stick 20c battery, also known as a "nunchuck" or "crane stock" type, is widely available for purchase online from airsoft retailers. This battery is designed for airsoft replicas and other RC hobbies, featuring high power density and a stable discharge rate. 
 
Specifications
According to the manufacturer NUPROL's website and product listings, the battery has the following specifications: 
Chemistry: LiPo - Lithium Polymer
Capacity: 1600mAh
Voltage (Cell Count): 7.4v (2S)
Continuous Discharge Rate: 20C @ 32A
Burst Discharge Rate: 40C @ 64A
Configuration: "Nunchuck" or "Double Stick" style, with two separate cells
Dimensions (each cell): Approximately 7 x 30 x 92 mm
Connector: Available with Small Tamiya or Deans (T) Connector, depending on the specific product variant. 
Important Safety Information
When using LiPo batteries, it is crucial to follow specific safety instructions to prevent damage, fire, or explosion: 
Charger: Always use a specific LiPo balance charger and connect the balance lead when charging.
Charging Location: Always use a fire-retardant safe-charging-bag and never leave the battery unattended during charging.
Voltage Levels: Do not "run-flat" the battery, as this can cause permanent damage. Check cell voltages before and after charging, ensuring they stay within the 3.3V minimum and 4.2V maximum per cell range.
Storage and Condition: Store at an optimal charge level (around 60%) if not in use for long periods. Stop using the battery immediately if the cells show signs of swelling, expansion, or damage.