I wanted an insert for the Praki containers (used for filament storage) that consumed less material, didn't bind the hydrometer so much, and was easier to remove.
This one takes a bit less than half the filament and also has a notch in back to assist with removal at different angles.
Also, the hydrometer is easier to get in and out.
The design has a few bumps on the exterior - points of a hexagon that are filleted over. The intent was to allow the object to friction fit tight enough to handle a direct smack on the lid from above. These managed, but if it's not strong enough for you, just cut the fillet down a little more.
Should be fine to print…
Printed on a Bambu A1 Mini.
In theory, the F3D file's parameters can be tweaked for different square-shaped hydrometers, but I have only tested the Tasogen ones.
The author remixed this model.