High quality anodized aluminum Step Up Ring made in JAPAN. This is for mounting a 58mm filter or hood on a 48mm lens front ring. The ring converts your 58mm filter ring to a 48mm size. Step up/down rings like this are a good idea. Filters and hoods can be very expensive so these rings save you a lot of money. I like having the ability to use all of my filters and hoods on all of my lenses.