S = 100-Pack, M = 250-Pack. The product comes in a sturdy, professionally designed box with an elegant appearance and a premium tactile feel. Self-Sealing Design: These 10x13-inch envelopes feature a strong adhesive strip for effortless sealing-simply peel off the backing strip and press down the flap to secure; no licking or moistening is required, offering a convenient and efficient solution for bulk mailings. Privacy and Security: Our mailing envelopes are crafted from high-quality, extra-thick 100 Gsm white paper, boasting exceptional resistance to tearing, breakage, and punctures. The opaque, heavyweight material effectively conceals the contents inside, ensuring complete protection for your shipments. Weight: 4.38 lbs.