This buckle can be used is multiple situations. My design is simple to print and is of low cost and designed to accept a flat woven strap of up to 20mm width.
The strength of these buckles can be improved by choosing strong plastics. Note that there needs to be some give in the plastic to allow the buckle to flex, hence carbon fibre based filaments may not do well.
The buckle is a common 20mm size, but you can also experiment and scale the buckle to your needs via your slicer software.
My print is made in eSUN PLA+ filament, with 0.2mm layer height and 15% infill on a Bambu Lab X1 Carbon printer. Inner supports are needed for the female part. See 3MF file.
I hope that you can find this print useful, too.
Remember to leave me some feedback or even a tip to keep me enthused to make more of these drawings.
For my latest models, see my main uploads site: https://makerworld.com/en/u/3687936443