This Cokin Adapter Ring for the X-PRO series allows you to attach the Cokin Filter Holder BX-100A to a lens with a filter diameter of 67mm.
Cokin X-PRO series
The X-PRO series from Cokin is aimed at professional photographers. The "X-PRO Series" filters are recommended for use on lenses with a filter diameter between 62 mm and 112 mm. The filters have a size of 130 x 170 mm.