The filters to be attached to the lens usually have ‘male and female threads of the same size’.

 

 

If it’s a 30.5mm filter, both would be labeled as M30.5mm. Therefore, you can stack multiple filters of the same size and use them together

 

 

Of course, it can also be attached to a 30.5mm lens. In the case of a universal lens, since the lens side has a female thread, you would attach the male threaded side of the filter.。

 

 

 

 

If you need to change the diameter, conversion rings like the following are available.

(The following is a ring for attaching a 37mm filter to a 28mm diameter lens.)