The Samsung 40T outperforms every 18650 and 20700 in regulated devices at up to about 20A-25A (60-75W). It's a wonderful balance between power and capacity, and is currently among the top 21700 cells on the market as of October 2018!
Flat Top Dimensions : 70.2mm (L) x 21.1mm (D)
Weight : ~66.87g
Typical Capacity : 4000mAh
Protected: NO, UNPROTECTED
Max Continuous Discharge Rate: 35A
Voltage : 3.6V
Full Charge Voltage : 4.2V
Price is per battery.