I had been hesitating for a while between several brands to choose a filter holder for ND and GND filters. I took advantage of a flash sale to buy this kit. I am not disappointed.
The whole thing seems sturdy and easy to store.
The case, quite pretty, has 5 compartments, 3 of which, for square ND filters, are lifted by means of a ribbon. On the back of the case, there is a ring to pass a strap and a belt passage. I would have liked a slightly more spacious compartment to accommodate the adapter rings with the CPL filter when it is dismantled.
The assembly (or disassembly) of the elements is well explained in instructions in several languages, including French.

Main positive points:
No color cast, nor loss of sharpness on the first tests carried out.
The plastic frame with its tabs to handle the ND filters.
The system for placing the CPL filter on the filter holder.
the knurled knob for mounting the adapter ring and the rotating housing of the filter holder.
The very accessible wheel for controlling the polarizing filter.
The strong hold of the square filter on the filter holder.
The robustness of the metal filter holder.