I use one on a Pentax 24-70mm filter size 82mm. Just make sure you buy the right size for your lens. I have the nd1000, and I am very happy with result. They also sell adaptor step down for your other lens. 

We installed it on our Canon RF 24-105 lens and it was possible to use the lens hood on this lens because the lens hood attaches to the lens via the bayonette mount which is on the outside of the lens diameter and the magnetic filter adapter screws into the thread on the inside of the lens. 

It last all day for me about 12 hours 

12v 

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.