From Manufacturer
This 67-82mm JetMag Pro Magnetic Adapter Ring from NiSi is designed for use with their JetMag Pro magnetic filter system. Once screwed onto the 67mm front thread of your lens, this adapter allows you to magnetically attach the 82mm filters of the JetMag Pro system. This means you can swap filters quickly 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.