Hoya Filters Magnetic Instant Action Conversion Ring - For Filters

Pretty cool

An inexpensive and simple way to convert your existing screw-in filters to a magnetic system that is much easier to use. I will likely use my filters much more often now.

The extra depth leads to vignetting on my 21mm Zeiss Loxia with 52mm filter ring so I'll use the adapter rings on a different 52mm filter size lens.