These Triangle Gym Rings are optimized for a nice flat bar to grip onto and minimizing material. The download includes two sizes, and even the small size (pictured in blue) should work well for most users (pull-ups and hanging exercises). I also have more standard gymnastics rings available here which may be preferred for muscle-ups and other gymnastics exercises.

Printing Guide

• 0.4mm nozzle, 0.2mm layer height, 8 walls/perimeters, 3mm top and bottom layers, 30% gyroid infill (or greater depending on the user)
• I printed using ASA filament because these are designed for outdoor use, plus the potential for acetone smoothing)
• A generous brim can be useful to prevent warping up from the print bed

Post Processing

• The bottom is flat with a 45 degree wall for printing without supports, so you may want to sand down that hard edge after printing (as well as the entire surface to smooth out layer lines, etc.). A metal rasp works well for initial rounding. Wet sand with 80 grit sandpaper for extra smoothing.
• Acetone smoothing ASA and ABS prints afterward can also create a very smooth surface and increase strength.
• You can hang these using purpose-built ring straps for adjustability but I went with these 60cm Nylon Climbing Slings that happened to be the perfect length for my mounting spot, plus they're very affordable. See images for an idea of how I hang things up without any extra hardware.
• Some people also like using silicone tape for grip, depending on the kind of training you're doing.

Also, check out these purpose-built hooks for storing the rings out of the way :)

Photographed model was printed using QIDI ASA Green (Amazon) on the Qidi Plus4 3D Printer (Also on Amazon).