This is a classical strap buckle as can be found on backpacks and other kind of low-load applications. The commercial, injection molded buckles of this kind are cheap to buy online. But hey, why buy if you can print in your favorite color? 

I just noticed that I did not see such a classical buckle in the strings and straps contest yet. Likely because all the designs were published before already. So here is my version of a freshly designed buckle for the common one-inch straps. 

This design can be easily printed without supports and will work out-of-printer. Simply print both parts in the uploaded orientation. PETG is clearly preferable due to its flexibility. I recommend 4 perimeters and 100% infill. 

If you want a really cool buckle I recommend this “secret unlock mechanism” design: [https://www.printables.com/model/565652](https://www.printables.com/model/565652)

For a no-nonsense buckle mechanism, which is really tough and strong but not that quickly to open and close, I still favor the double D-ring principle. It is no coincidence that premium helmet makers still use it until today. 

Get your double D-ring buckle here for 20mm straps:
[https://www.printables.com/model/415716](https://www.printables.com/model/415716) 

…and here for regular one-inch straps:
[https://www.printables.com/model/121235](https://www.printables.com/model/121235)

You need the strap tensioner shown in the pictures to adjust the length of your straps? You can find them with double D-ring designs in the links stated above. 

Happy printing!