This is the included Balancing Ring and lens hood that come with the standard (Panasonic) lens on the Zenmuse X5 or X5R camera. It's screwed onto the filter thread of the lens to help balance and stabilise the camera on the gimbal. It's also identical to the ring and hood that come packaged with the Olympus 25mm lens. The ring uses the 46mm filter thread on the lens so it will also fit the Olympus 17mm prime lens. It features an external thread for mounting a filter on top.