This small adapter can make it possible to use a light duty electric screwdriver with your Hario coffee grinder mill. The model this unit was designed for was the MSS-1, but presumably this should work with other mills with the pentagonal handle post. I used a Ryobi Tek4 screwdriver with the clutch set to 12 and speed to 1, and it ground coffee fine without risking damaging the mill. This was designed to be used with common sense and a small electric driver. We have had good results with both of the above. As always, if you encounter any problems with the design or have any suggestions or improvements, let me know in the comments.Made the unit with 3 shells, 50 infill and .2mm layers. It seems sturdy enough for its job with these settings.