The size of the adapter ring depends on the size of the filter thread of the lens used. This is noted on the lens and in the lens cap. 

Metal 

The benefit of this adapter is that it’s suitable for Pentax DA lenses that don’t have an aperture ring. The silver ring on the adapter controls the aperture linkage on the back of the lens. Although a lens might typically have a aperture range of f2.8 to f22, the adapter only has 5 stops, and the real value of the aperture is guesswork, however a mft camera will have no trouble gaining the correct exposure. Lenses with their own aperture ring can still be used on this adapter, you just need to see the adapter to ‘open’. 

I have used one on a Sony a7 mkii. 

It can't not be fixed well with the lens without the adapter ring. you should buy another adapter ring of 95mm size if you want to make this square filter fixed on the lens.