Save your thumb! This is a simple speed loader for 380 Auto micro pistol single-stack magazines. It works well with the Taurus Spectrum, Bersa Thunder 380CC model, and probably other 6 - 10 round micro 380 pistols.
You can use just about any nozzle or layer size, not much is critical when printing, but either use support, or print it bottom up so that the “thumb” prong carrier-pushing part stays clean. Trim and clean the inside with a knife/tool before use so you don't get little bits of meltable plastic in your magazine, and ensure that the prong moves cleanly into the magazine and presses the top round into the magazine so that another round can be more easily dropped inside.
The author hasn't provided the model origin yet.