Built-in USB-C Rechargeable Battery is a 16340 Li-ion battery
with a protection circuit in the anode  to  help  prevent  short
circuits, overcharge/discharge and overheating.

This battery has its own USB Type-C charging port for quick and
easy  charging  without  the  need  for  a  separate  charger.  The
battery  also  includes  multiple  levels  of  protection  including
overcharge protection, overheat  protection,  and  pressure  relief
vents which expel waste gas in the rare case of an  internal  short
circuit preventing an explosion.

Features:

• Built-in USB-C Rechargeable Battery
• Size: 16340 Button Top Battery
• 800mAh Nominal Capacity
• 3.6V Nominal Voltage
• Charging current: 0.6A
• Charging current by USB port: 0.5A
• Protection Circuit in the Anode to prevent short circuit
• Multiple layers of protection
• 500  charge  cycles  can  be  expected from a  properly 
  maintained battery
• Fully covered with a steel  shell  for  impact  resistance
• Overcharge,  discharge,  short  circuit,  and overheating
  protection
• Three sets of over-head  protection:  Pressure  relief 
  valve  protection, separate microporous protection, and
  PTC cathodal block protection
• Indicator  light  on  battery  is  red while charging, blue
  when charged

Specifications:

• Weight: 18.8g
• Size:
  Length: 35mm 
• Diameter: 16.7mm
• Designed to work with:  PD25R, LD15R, E18R  V2.0,
  and HM50R V2.0.