The lid fits nice and snug and the seal is tight and it holds dry tea safely. However, you get the usual little powder mess when opening the lid. 

The idea is to transport dry tea or moist tea grounds without water. I don't know (yet) if it would be watertight with some water left in the calabash.

Update 2024-08-03: 

I was never fully satisfied by the oval shape of the lid, it was tilting around on my desk and I was also missing a simple stand when I was on the go. Therefore, I created another iteration, adding fins inspired by Mate Mateo Touch. The stand is not as sturdy as w00h's https://www.printables.com/model/915091-mate-mateo-stand-20 but it fits the purpose. It can also be used during preparation to keep the calabash in a tilted position. To top it off, it now prints with minimal support for the fins, which results in a far nicer finish on both sides, not trapping as much mate powder as before.