m4 pins
thingiverse
Airsoft M4 receiver pin scale it to 0.50 and sand it and your good to go . using Cura.
Download Model from thingiverse
With this file you will be able to print m4 pins with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on m4 pins.