Q
Can you add slots to the filter holder so you can hold three filters?
Answer Question
A
No. This filter holder can only hold 2 filters. I believe the more prudent course would be to get a filter that is rated for more stops and can replace two filters that are rated for less stops. There are filter holders that do hold 3 filters but they are smaller than the K&F filter holder (which is 100 x 100 mm). And in my opinion, the quality of those 3 fitter holders that are located on Amazon is less than the K&F system.