The NiSi 72mm Metal Stack Caps are a set of top and bottom durable metal caps to fit 72mm filters. Simply screw your filters together then screw the stack caps on the top and bottom. The NiSi 72mm Metal Stack Caps can be used with a minimum of 1 x 72mm filter and can be used to protect 20+ 72mm filters screwed together. The metal construction offers protection to filter surfaces and protects the filters from dust, scratches and fingerprints while not in use. The Stack Caps enable a more organized, streamlined system for storing and carrying your circular filters.