Used for several months. I am selling it because I no longer use it after changing my smartphone. There is no rust, so I think it's mainly aluminum, and the screws are stainless steel. MINOURA Accessory Holder [SGS-300S] φ22-29mm compatible Silver Diameter 22-29mm compatible Length of the horizontal bar: 100mm Diameter: 22mm Can hold 3 items For general handlebars and seatposts By changing the attachment of the red arm by 90 degrees, you can easily switch from the handlebar style to the seatpost style.