Upgrade one:

1st gear is for resistance, suitable for screw disassembly; 2nd gear is high-grade, suitable for flat drilling
Upgrade two:

5-7: Elastic screws
10-13: Wood
16-19: Tile
22-25: Steel
Upgrade three:

Infinitely variable speed switch: It is easy to adjust the speed by pressing the switch light and heavy.
Upgrade four:
Porous excellent heat dissipation, long-term operation does not burn machine
Upgrade five:
Waterproof and fall-proof, pamper your careless