From Ammoland:

Almost all prints can be accomplished with these inexpensive machines. Most of those in the 3D-printed gun world use PLA+ filament for printing medium. The material can be as cheap as $20 for a 1kg spool. One spool can allow the user to print a massive number of items, including Hoffman Tactical’s forced reset trigger. The 3D-printed parts of the forced reset trigger only cost a few pennies to print, although a spring and roll pin is needed to complete the trigger.