I made this for an animal shelter.  Room to Dremel your pet's name on the collar.  Modeled in Blender.  I print it in PLA, because it is eco-friendly, but can be printed in a material of your choice.  .4 mil nozzle.  After print is complete, normal, light post processing is needed.  Paint if you desire.   After post processing, insert a normal, metal keychain ring with with a soldering iron on the flat bottom side.