12mm Aixiz Laser To 20mm PROXXON Adapter
If you have a laser in a common 12mm "Aixiz" enclosure, this part can make it fit into your 20mm PROXXON mount on a CNC machine or whatever.
https://www.youtube.com/watch?v=5Ztl6tL9gxg&feature=youtu.be
In order to use it with the "Mostly Printed CNC -Add On- Dremel 300 mount" you have to sand the bore to 20mm...
Here is a guide on how to set up a laser gcode script: http://jtechphotonics.com/?page_id=2012