Common Envelope Sizes

DL - 110 x 220mm to fit letterhead folded into 3 sections

DLX - 120 x 235mm to fit multiple pages or a DL booklet

C4 - 324 x 229mm to fit a flat A4 sheet

C5 - 229 x 162mm to fit a flat A5 sheet

B4 - 353 x 250mm

11B - 90 x 145mm inserted inside a DL envelope and used, for example, for reply paid purposes.