The Sensei 49mm Filter Stack Caps consists of a set of top and bottom durable metal caps to fit 49mm filters. They will protect the filters from dust, scratches and fingerprints while not in use. Simply screw your filters together then screw the stack caps on the top and bottom. Additionally, these caps enable a more organized, streamlined system for storing and carrying your filters.
I used to carry my filters in indicidual hard cases when out doing landscape photography. But this was a pain because of the volume of all those cases and trying to find individual filters in a pile of cases. With the filter caps my filters are neatly organized, take up little space in the camera bag, and easy to find.
This is a screw on lens cap. It takes a second or two to put it on or take it off, but it won't come off on its own, like the standard pinch type often does. It looks great on the camera as well. I wanted the lens cap, not the filter stack caps, but the former was out of stock, and the latter does the same job. That being said, it would also work great as filter storage. I've been using Sensei lens caps for 5 years on three different cameras and am very happy with them.