The Sinar Bellows Holder can be mounted on to the front portion of a lens by using a lens adapter ring.It supports one filter of 100 x 100 x 1mm and one Sinar bellows with a 100mm frameYou can attach 100mm neutral density filter or a special effect filter to the front of the lens with this bellows holderThe Sinar Bellows Holder helps build a bellows lens hood