The Dovpo Punisher 90 has to be the most compact 21700 compatible box mod on the market at the moment. It delivers up to 90W of power. 
With an independent Menu Button, it's way easier for you to go through menu and settings. 
1. Size: 82.5mm x 26.0mm x 42.0mm
2. Material: Zinc Alloy
3. Battery: 21700, 20700, 18650
4. Color: Black, Red, Green, Blue, Purple
5. Thread: 510
6. Input Voltage: 3.2v - 4.2v
7. Wattage Range: 5.0W - 90.0W
8. Resistance Range(Non-Temp Control): 0.08Ω - 3.50Ω
9. Resistance Range(Temp Control): 0.08Ω - 3.00Ω
10. Temperature Range: 200°F - 600°F/93°C - 315°C
11. Working Mode: Wattage/ByPass/Ni200/Ti/Ss316L
12. Battery Charging: 1.5A
13. Multiple Safety Features