Commercial: for commercial correspondence with or without window to reveal name & address pretyped on folded enclosure. The opening can be on the long side (banker’s) or short side (pocket).

Baronial: more formal envelope with deep pointed flap.

Self-sealing closure: with removable or permanent adhesive strip on flap for automatic sealing.

Gummed closure: with dry glue applied to flap which is activated with moisture to seal envelope.

Clasp or String & Button closure: permit postal inspection and serve well as weighty or bulky mailers.

Expansion: for bulky correspondence.