52mm ND Filter ND1000 (10 Stop) Lens Filter 28 Multi-Layer Coatings Waterproof Scratch Resistant Super Slim for Camera Lens (Nano-X Series)

SKU: KF01.1002

A
hello, this is not variable nd filter, it just nd1000 filter, it is 10stop, 
A
Yes, just as any filter I have, they all accept manufacturers and after markets caps and more can be threaded on in front and behind. No loose band. Well built. 
A
No I don't think it will fit any Gopro not unless it's specifically made for it. This size fits a 58mm lens thread and the Gopro has a much smaller size lens.