This is a true perfect solution for the ultra wide-angle, large & medium format photography, the push on filter holder is designed to fit directly onto lenses, & has an outside barrel diameter of 100mm. The holder attaches directly onto the lens itself & such close proximity allows the maximum possible angle of view without vignetting. Custom adaptor donuts are available to enable fixing to smaller lenses. The unit also has added advantage of using standard 100mm filters. Note this holder will not work with Lee Filter Adapters.