We don't have any B5 envelopes anymore at work since many years, because it costs the same to send B4 as it would be to send B5. And as long as 99,9999% of our letters are in A4, it was an easy decision.
In Germany there are the degrees
- postcard
- standard letter (20g)
- standard letter heavy
- big letter (up to B4)
- big letter heavy (up to 2000 g).
And to make it cheaper, there are special tarifs for sending printed information in an not closed envelope or for sending books up to 1000 g. But I'm afraid the club will not save any money at all, if the newsletter was transfered in a parcel to Germany and sent from here. (In fact, some German companies are sending their post from the Netherlands to save some money.)