This is a cap for a standard 1 gallon carboy to hold the rubber stopper in place during fermentation. This is compatible with carboys that use the 38mm thread size. I used the #6 or #6.5 stopper for my carboy and this fits both. If you have issues with stoppers popping out randomly then you'll definitely want this accessory.

Creality

Ender 3

No

No

.08mm layer height

50%

This shouldn't require supports as the threads are relatively skinny and are filleted.