From Manufacturer
This JetMag Pro Magnetic Adapter Ring from NiSi is designed for use with their JetMag Pro magnetic filter system. Once screwed onto the 52mm front thread of your lens, this adapter allows you to magnetically attach the 67mm filters of the JetMag Pro system. This allows you to quickly swap filters on the go to suit your needs or create your desired look. Its aluminum construction makes it highly durable, and the slim design prevents vignetting in your images.