A simple concept. You have a filter or other lens accessory which screws into a 55mm thread, but your lens is a 52mm thread. These rings provide a female thread that adapts your accessory and a male thread that screws into your lens. This allows you to mix filters and other accessories on various lenses that may have different size accessory threaded sizes. Made of black anodized aluminum in Japan. Many different sizes available and in stock for immediate delivery.