Safer snap cap than just 3d printed - uses 22lr casing to protect your firearm.
Insert into a spent casing, may need to lightly use a hammer.
Can be reused a number of times but the casing will eventually wear out. Can usually remove and re-use the printed piece by heating the casing. Cheap and easy to print either way.
Two printing plates are in my profile. One with 20 snap caps and one with 10 for you to choose the quantity desited.
I recommend printing with a brim as in my profile. Otherwise settings are pretty forgiving.
Real credit goes to YayBacon for his model on Thingiverse. All I really did was arrange the plates with different quantities and set up the print profile. He did the hard work.