Peak Design Mobile Mount - Universal Adapter

Requires 4x 10mm x 3mm magnets and a pause at the appropriate layer to embed them in the print. (see the original instructions https://www.printables.com/cs/model/181005-peak-design-mobile-to-14-20-thread-with-magnets-an)

It uses the 1cm-uni-mount system, which consists of two holes spaced 1cm apart, allowing you to easily attach a different type of holder and thus create your own combination of connections. 

See more at https://www.printables.com/cs/search/models?q=tag:1cmunimount.

Modified for printing without supports and for better connection with the mobile phone.

You can attach various accessories, such as GoPro or Garmin mounts, using screws.