This is a dildo mount specifically designed to fit a behind barz male chastity belt. It's modeled to fit the standard belt, I'm not sure if it will work for the removable cage mod or the 3 lock kind, I don't have one to test. It's sized to fit a dildo with a circumference of ~5.25, or a girth of 1.6, with a flared base.
For printing, I recommend laying face up, with supports on. I printed it with 4 walls and 50% infill to make sure it's strong enough, this worked great its stiff and fully functional.