OP/TECH USA 0701581 Filter Cap 58mm Protects the lens/filter from dust, moisture or impact. Held in place by the filter of your choice. Additional filters can be added without having to remove the FILTER CAP. Available Sizes: 49mm, 52mm, 55mm, 58mm, 62mm and 67mm. The FILTER CAP is held in place by any optional filter you select As it's positioned behind the filter, it enables other filters to be stacked on top, without causing vignetting Effectively blocks out dust and moisture Also provides impact protection to the filter rim and lens ? common damage points for avid photographers A unique product from a unique American company