This model was purpose designed to connect a disc golf suction cup retriever (with an M5 bolt) to a Kwik Stik XXL (which is M6 bolt compatible).

This adapter's application can extend beyond this use case, although it is worth mentioning that due to the size of M6 and M5, the resulting print strength may not be adequate for all applications. I printed with 90% infill to reduce torsion weakness between the threaded/bolt part and the hex part of the adapter.

Thanks to Keep Making - YouTube for making a very useful and powerful Blender add-on called Precision Bolts [ Addon ] (gumroad.com), which allowed me to create the 3D model very quickly (in less than 30 minutes) in Blender and be able to fine tune adjustments easily because of its parametric qualities (e.g., length of parts).