Flat Flange: Both flat flange and blind flange must feature a ‌Flat Face (FF)‌ surface finish, characterized by a smooth,
                   flat sealing surface without any raised or recessed features. 

‌Neck Flange: The neck flange is specified to have a ‌Raised Face (RF)‌ surface finish, which includes a raised sealing surface with a ‌serrated texture‌.