Appreciate "Axel Johansson" did the "Strength test" at this design. Check the film on youtube https://www.youtube.com/watch?v=WayVij-MZDE Here's the info of the film and the test result Measuring of the maximum force the carabiner "Strong Flex door Carabiner" from thingiverse can handle. Measured maximum force: 236 N The carabiner is printed in ABS. The design is Charlie1982's: http://www.thingiverse.com/thing:489709 Infill: 100% layer height: 0.15 mm Temperature: 245 °C Total print time: 1:22 h Thousands of thanks Axel did the test and sharing the result :D Carabiner is very useful to me, I make the design by 3D print can let the door feel like spring inside. The design can print without support and raft. Layer high from 0.15mm~0.3mm is fine. Infill better to use over 70%. Here is the video link: http://youtu.be/f-gohLbARMo Hope you will like it ;)