Samsung 25r would be the most used batteries in the vaping world. Readily available and great balance of performance and capacity make this a great choice for most.
Model Number: INR18650-25R
Nominal Capacity: 2500 mAh
Nominal Voltage: 3.6V
Discharge End Voltage: 2.5V
Standard Charging Current: 1.25A
Charging Voltage: 4.20+-0.05V
Max. Continuous Discharging Current: 20A.
Note: Batteries will only have test charge. Ensure that before use that batteries are charged to reach full capacity. Failure to do so may lead to long term cell issues.