Using stack caps is the best way to keep your same size camera filters, clean and ready for use. The stacks of camera filters, take up the least amount of space in your camera bag. The Stack-Caps are 2 covers, finished black just like your camera filters, They stack-caps are made out of metal and are attached by screwing into the front threads of the filters. The rear cap, then screws into the bottom of the stack of filters. Available Size :25mm through 86mm.