Junction box for ceiling lamps

I was in need of one and wanted to save a trip to the hardware store. Prints without supports and screws together nicely.

I didn't put any holes, just used a drill where necessary. Just be careful with PLA since it's quite brittle and kind of a pain to drill into. Start small and work your way up. 

If you don't want to or don't have a drill you could also use a cylinder modifier in prusa slicer.