Ampac tamper evident envelopes feature a tear off redemption slip which provides you with a sequential number allowing you to track or trace your envelope the double seal displays a void message if tampered with helping to keep items secure in transit this pack contains 20 c3 envelopes sequentially numbered envelopes for easy tracking 100 recyclable displays a visual message once open if tampered with size c3 335x430mm resistant to solvent based attack supplied in a pack of 20 opaque