That's fine. The polarizing filters also have a rotary thread on the front where the filter plug-in system can be attached. 

As K&F Concept ND2-ND400 filters adjusts the amount of light that can pass through with polarizing glass, a colour cast can't be avoided for all the variable ND filters on the market. However, K&F Concept variable ND filters are made by the best coating technology, which reduces the effect of the polarizing film on image color. *Based on our professional test, the colour cast of K&F Concept ND2-ND400 filters is around 290k while the industry standard is 500k. 

67mm should also be stenciled on the front edge of the lens somewhere. If so, then you should be good to go. It should be on the lens because a lens cap can be lost or broken. 

hello the K&F Concept Slim UV Filter + Slim Circular Polarizing Filter (CPL) + Neutral Density Filter + Slim FLD does not work for work for the solar eclipse 

If you polarizing filter is square and size is 100X100mm, the hold is okay for you