1. Special aviation aluminum alloy, high strength, impact resistance, twist and pressure. Machining process. 2. Surface treatment: high-mesh sand blasting machine and color quality pure matte black or silver. Ultra-low chemical residues, attached to a solid! Package Included:49mm-52mm Step-up ring x 152mm-55mm Step-up ring x 155mm-58mm Step-up ring x 158MM-62mm Step-up ring x 162mm-67mm Step-up ring x 167mm-72mm Step-up ring x 172mm-77mm Step-up ring x 1 Using Step Up And Step Down Rings To Take Better PicturesWhat is a step up ring Step up rings, also known as adaptor rings, allow you to use filters and accessories that are not the same size as your cameras lens. Lenses and filters come in a large range of types and sizes and unfortunately they don't always fit together correctly . Fortunately there is a step up or step down filter for just about any need. How step up rings work Step up rings provide a way to fit a larger diameter filter or accessory onto a smaller lens. The step up rings screws onto your lenses threading and provided a larger thread with with you can then attach other elements included more step up rings. How step down rings work Step down rings work in the exact same way but instead provide a way to attach smaller accessories and filters to larger lenses.It is important to note that typically, the farther away from the lens you place a filter the worse the optics will be. It is always best to look for the thinnest adaptor ring that you can find as these will keep the filter close to the lens .