FCW Semi Full Auto Sear And Selector Kit for KJ KC02 
 
Require necessary skill or modification to install and assemble
Please follow these steps:
1. Use a ruler, draw a horizontal line with the hole which parallels the trigger group with a 5.5mm diameter circle.
2. You will need to identify the spacing between semi and full auto. From the right side of the horizontal line, find the point 3mm around the circumference of the circle going downwards, then another 3 mm. 
3. After drawing the safe, semi and full auto points, use a drill and drill 3 holes on the surface for the ball bearings like the photo show. 
Photo 3,4 show that the sear replace the original parts
Photo 5 is the place that need to modifly if selecting fire is not smooth