This is a ball and socket joint designed to hold 4 neodymium magnets(3mm * 10mm), inspired by those magnetic car mount for phones you can buy on amazon/aliexpress https://goo.gl/5xJXiI.
fully 3d printable. The flat end was intended to be mounted with double sided tape.
Here are some spec...
Ball diameter: 17mm
Magnet dimensions: 3mm thick, 10mm diameter
Socket nut threading: none-standard thread, just made it strong enough as plastic part.