Haida 2 in 1 CPLVND Filter for Camera Pro II Multi-Coating Circular PolarizerVariable Neutral Density SLR Camera Lens Filter Waterproof Scratch Resistant Nano-Coating Filter 67mm

Taking the advice from most of professional photographers, the Variable ND was designed between 3 and 7 stops. All you need to do is to pull the small round lever to adjust the ND stops. If you want to use two functions at the same time, please remember to adjust the Variable ND filter firstly and then adjust the CPL filter.