Cokin B100A Filter Holder, Series X-pro 1 XP Filter Holder ONLY Accepts the XP Filters which are the Largest size Filters on the market - 170mm x 130mm (5 1/3 x 6 2/3") Holds 2 filters at once Exclusive Ring Locker System, which keeps the filter parallel to the lens and it allows you to secure the holder in a certain position or you can loosen it to allow the holder to rotate freely Large holder reduces risk of vignetting when shooting with wide angle lenses