It's recommended to buy the largest filter size and use it with the stop down filter ring on your other lens. Learn more about the step down ring here https://www.kentfaith.com/SKU0801_11-in-1-step-down-ring-set. 

Hello dear Karina, have a nice good evening. The color filters have a screw-in thread of 52 mm. The lens must have a thread for 52 mm at the front in order to attach the filters to the lens at the front. I hope I could help you. Good night. Mfg Osiris 

so it should be 55mm. 

no it will not the eos-r has a different mount 

I actually have not received this adapter yet. It's shipping from China. Don't think that was disclosed in the ad. However, I do not believe this is for the Pentax Q body rather for digital and film cameras that take the Pentax K mount in its many variations. So I'm expecting to be able to mount my Leica M mount lenses on my digital and film Pentax K mount cameras, no autofocus or relay of exposure information, only to be used with manual focus and exposure.