These New Guardian Armour gusset envelopes are made from durable, heavyweight 130gsm paper reinforced with woven polyester thread for additional strength. The manilla envelopes feature a simple peel and seal closure with Power-Tac adhesion for an extra strong bond and expanding 50mm gusset for mailing bulky items. These C4 envelopes are suitable for A4 documents. This pack contains 100 manilla envelopes.