The cokin x pro filter system consists of a rectangular plastic filter holder with three slots one for cokin x pro rotating filters and two for rectangulars a variety of optional adapter rings which can be locked into place by two retaining screws or rotated as well as many optical resin filters the x pro system adapter rings cover sizes from 62 112mm hasselblads b60 b70 and rolleis b6 these filters are particularly suited for todays ultra wide angle lenses ie 17 35mm cokin x pro