Since CO2 lasers are invisible to the human eye it is very tideous to calibrate the mirrors of the chinese K40 CO2 laser cutter. I made this nozzle to clip on the front of the laser tube. Inside the nozzle you can mount a small, regulated laser diode. I used a battery pack to power it with 4.5V which is enough to emit a strong visible red light. With help of the mount the laser will shine directly onto the mirrors and you are able to roughly adjust the mirrors for the CO2 laser.