The B+W 100mm Filter Holder is used for mounting your 100mm-wide and 2mm-thick filter. You may use this holder with a separately available adapter ring for conveniently fixing the filter on a compatible lens. This filter holder can be used for three filters at a time, thanks to the three pairs of filter slots that are attached by four screws that can be tightened and loosened as required. The holder has a pull-and-release locking system that ensures a secure attachment. Also, it allows you to rotate the holder at 360°, thus making it ideal for mounting graduated filters as well as other circular filters.