#10 Western Sulphite 2584 Regular Envelopes, 24 lb., Diagonal Seam, Box of 500. White commercial business envelopes with a smooth vellum finish 4-1/8 x 9-1/2". This envelope has a traditional full flap with diagonal seams and runs smoothly through postage meters. Flap is fully gummed and holds secure, moistening is required.