There is a front thread, allowing another filter to be installed in front of the microlight filter, as long as the caliber is the same. 

There is a front thread to allow another filter to be installed in front of the micro-light filter, as long as the caliber is the same. 

Yes. 

Yes, the filter has an external thread. A combination actually makes no sense because the permeability is regulated via the adjustment ring 

When you receive your item, please check your item carefully. If the package appears damaged, 
please complete the following steps:
1) Take a picture of the damage.
2) Then please email us at customer@kentfatih.com immediately and attach the photos.
3) We will contact you directly with the next steps.
4) DO NOT throw away the boxes or packaging materials, otherwise, your claim will not be honored by the shipping company.