There are several types of envelope design: Without window and with window (right or left).
Depending on the closing system used for the envelope, we can distinguish the following types of envelopes:
- Adhesive free
- Normal moistenable or gummed closure
- Silicone strip closure
Some of the envelopes have an easy opening system consisting of a perforated line on the flap that opens easily when pulled.
Envelopes of larger dimensions and side closure are generically called bags. That is, while envelopes have the opening on the long side, bags open on the short side.
According to their flaps, we find the following classification:
- Contour flap or classic envelope: Triangle-shaped flaps.
- Konstancia envelope: Straight flap, trapezoidal flap or rounded flap.