Hi, you can attach center-pinch lens cap on this filter , except the ND1000 filter , the CPL, UV and magnetic adapter ring can attach lens cap. 

Hello! If you use the magnetic UV filter separately, or use the magnetic adapter ring together with the CPL filter, you can use a normal lens hood on it. Does not require a larger thread. If you use the magnetic adapter ring together with the ND1000 filter, you cannot use another lens hood on it. 

1. The UV filter can be used alone. ND and CPL need a matching magnetic adapter ring, because the camera lens itself is not magnetic and cannot be directly attracted to ND and CPL 

It is a normal phenomenon if you want to use ND filters together or ND filter with other filter, like ND2+ND4,ND4+ND8,ND2+ND8 or ND2+4+8,ND filter+UV, the photo effect will become to light pink color, you could set "white balance" as "AUTO" to improve it, but will not be completely disappeared. 

For this series, front thread diameter is bigger than the back thread diameter.
for example:
Back thread diameter (attach to lens): 40.5mm
Front thread diameter (attach additional filter/other accessories): 43mm
Variable ND filter size other accessories size

37mm	40.5mm
40.5mm	43mm
43mm	46mm
46mm	49mm
49mm	52mm
52mm	55mm
55mm	58mm
58mm	62mm
62mm	67mm
67mm	72mm
72mm	77mm
77mm	82mm
82mm	86mm