stratic Itis not computer related. It can use any micro USB power source for recharging. A computer is required only if you want to flash a new firmware. This is a very rare, dangerous and very advanced operation. If necessary, this can be done with any computer that is able to read and write on an USB storage key.

stratic One is not better than the other. They have different characteristics. The 120 is slower (170rpm) but it has more torque (2.8kgf/cm). The 121 is faster (380rpm) but it has less torque (1.5gf/cm). One is fast, the other is strong, but they deliver equivalent power. Perhaps that the 121 is more efficient for daily work. When a screw is strong, with the 121 (like with the 120) you can always start the first turn by hand and then finish very quickly by pressing the button. The 120 can unscrew stronger screws in automatic mode but at a maximum speed of 3 turns per second, when the 121 provides a bit more than 6 turns per second. Generally, if a screw is strong, it's only during few degrees on the first turn. And if it is very strong, there is more risk to damage it, so it's better to do it slowly in manual mode.