Step-down rings are filter adapters that let you mount a smaller filter on a lens with a larger thread. This category offers Fotocom and Gloxy step-down rings in a very wide range of size combinations.

A ring is chosen by two sizes: the first is the lens thread diameter, the second the filter diameter, for example 72–58 mm or 52–49 mm. This lets you use one filter set across several lenses. Keep in mind that a smaller filter, especially on wide-angle lenses, can cause vignetting in the corners of the frame, so large size differences are best used with longer focal length lenses.