My mom likes to stack mason jars but it gets kind of dangerous with regular mouth mason jars especially. She saw some commercial products for stacking them and easier organization, but I couldn't find a 3d print that met her needs. I'm somewhat new still to 3d modeling but decided to give it a try.
 

The idea was to create a modular system for stacking mason jars stably with room to expand the top and bottom sections to allow for various sized jars and mouths.
 

I printed a bunch in PLA and they have held up for the last couple of weeks, but PETG or ABS/ASA might be better for long-term storage. Parts are split to require no supports and can be stuck together with pegs and glue, or you can size the pegs up for a friction fit to make things easier.
 

If you have any suggestions for improvements or would like to see another size of mason jar, please feel free to leave a comment and let me know. I would appreciate it :) I mostly had access to Kerr jars as that is what my mom primarily uses, but I found that even among those jars some of them fit snugly and others had a bit more room.