Fotasy MLC 40.5 mm Camera Filter Stack Caps (Black) This item can work as a 40.5mm Metal Screw-in Lens Cap, and it can also work as a 40.5mm Filter Stack Case. Filter case protect filters from dust and scratches while they are not being used Simply screw the filters together, then screw these stack caps on the top and bottom. Compatible to lens with 40.5mm thread size, and 40.5mm Filters