A spacer made for 3g Cake carts(and probably others) so that you can screw them onto any battery without having to worry about blocking the airholes that are right ontop of the 510 threads.
This was designed with a 1mm spacing between the 510 threads and airholes.
Printed on an Ender 3 using a 0.2 nozzle.
The author marked this model as their own original creation.