knew that there was no industry standard in these magnetic filter specifications, and so magnetic filters (and also magnetic thread adapter rings and magnetic lens caps) from different manufacturers don't always "stick" when mixed together. So I was concerned whether this K&F magnetic CPL filter and K&F magnetic thread adapter ring are compatible with the Urth-brand magnetic filters and a magnetic thread adapter that I already was using. I am happy to report that, at least in this 77mm filter size that I tested, the K&F and Urth magnetic filters seem totally compatible / interchangeable: - I was able to attach Urth magnetic filters to this K&F magnetic thread adapter - I was able to attach this K&F CPL filter to an Urth magnetic thread adapter. - I was able to stack the K&F and Urth filters magnetically Aside from the magnetic properties, this K&F CPL filter seem to work as expected. It has nice and even anti-reflection coatings, and didn't seem to impart any offensive/unexpected color cast as it removed glare from shiny leaves and darkened blue sky. I have no complaints. So I would like to give this K&F magnetic CPL filter + magnetic thread adapter 5 stars.