It has been mentioned on one forum that Ostara filters have “soft” thread , and do not screw in to eyepieces very well.
I can assure you this is not the case. I have sold well over 1000 of these, with no issues from any of my buyers.
I check them regularly , and never found any problem.
It is more likely , that the issue may be with some inferior eyepieces that do not have strong inner thread, or the person using the filter has simply cross threaded
Ostara filters can be bought from Northern Optics
The Ostara Moon / Skyglow filter does what it says on the tin. It reduces some light reaching the eye, so cutting glare and improving contrast. The filters also helps reduce sodium light (street lights) for better deep sky observations.
If you have no light pollution, but simply want a good Moon filter, go for the Ostara Crystalview filter. This version gives a more neutral colour than the Moon / Skyglow