I wanted a filament runout sensor housing that would fit the z limit switch that came with my Anet a8. I found the arm on the sensor was a little longer than the other models out there so I came up with this. I set the tolerances to be 0.2mm so that the lid is a tight fit but not impossible to take back off. Also limited the length of area the filament runs through to reduce drag. Both parts should be printed flat side down.
You can use as little as 10% infill, but the top layer near the sensor will sag down. I went with 50% to prevent it, but it isnt a big deal either way.