The Hoya 67-72mm Step-Up Ring is a reliable and economical way to use filters. For example, a 49-52mm Step-Up ring would allow you to use 52 mm filters on lenses with a 49 mm front filter thread size.
Note: Hoya also produces Step-Down Rings which allow smaller sized filters to be used on lenses with larger front filter thread sizes. For example, a 52-49 mm Step-Down Ring would allow a 49mm filter to be used on a lens with a front filter thread size of 52mm. Care must be taken using Step-Down rings in order to avoid vignetting.
Small, efficient way to save space and money at the same time
Allows user to buy fewer filters but continue to shoot the images they want