Envelopes are usually available with three different types of seals. In order to avoid any confusion, here is a short explanation of the most used terms:
What is the difference between envelopes on the one hand and mailers on the other? An envelope on which the flap is on the short side is called a mailer; if the straight or pointed flap is on the long side it is called an envelope.
The most common sizes of envelopes are as follows:
DIN C6 114 x 162 mm
DIN B6 125 x 176 mm
DIN long 110 x 220 mm
DIN C6/5* 114 x 229 mm
*somewhat larger and more easily machine-filled than DIN long
Size and position of the DIN window: The size of the window is 45 x 90 mm and its position on the broad format version is on the left (flap at the top) with a 15 mm margin from the top and 20 mm margin from the left side.
Because the post office is constantly changing the maximum size and limitation parameters, we refer you here to the hopefully always current Deutsche Post webpage: www.deutschepost.de. There you can also consult the German post office postage calculator (only in German although some info in English can be found on the Internet).
Similar webpages for other countries can be easily found in the Internet…