You can wear it when you want sport your wedding band without messing up the real one sitting in your sock drawer. It's made from a brass compression fitting
The fittings come in all kinds of sizes so you may not even have to hammer it out. I had to. Notice that before, the fitting would only pass my first knuckle. Just look at the hardware store. Paint the inside of the ring with nail polish if your going to wear it for an extended period of time. Brass is made with copper so it's prone to turn your skin green.
I took a photo of the polished brass next to my gold wedding ring. They look pretty simillar.
For further on polishing see:
For further on resizing see: