Plus Fabric C4 Gusset Envelopes are the professional choice for business mailing. Made from bright white 120gsm paper for strength and quality, these envelopes feature a secure peel and seal flap for secure closure: just remove the protective tape and fold down the flap for a strong closure. Power-Tac adhesive provides a long lasting seal that helps to protect your documents. Theyre ideally sized for unfolded A4 documents, with an expanding gusset to hold contents up to 25mm thick.