Push and Plug fastening

You push and plug these two, and they're locked on all three axis. Well, that's the theory. It needs perfecting. It's particularly very resistant to being pulled out straight. I'm sure you could attach 20kg or 30kg easily. It works best with 20mm for each part, or 4cm total (~2.2cm when plugged). The utility is that you can add it to your 3D models, and then easily plug one in another. It kinda works at 10mm, but it's a bit flimsy. I'm a beginner modeler.

I admit that in small size it prints