Western Sulphite® Open Side Booklet Open Side Booklets have their opening on the long dimension - offering inserting ease and convenience. These envelopes are manufactured with white wove SFI Certified paper, two side seams under construction and a traditional remoistening seal.White Sulphite (SFI CERTIFIED) 92% Brightness Vellum Finish Two Side Seams Under No Window Remoistening Seal Flap Down