Plain envelopes are letters. They are not small parcels and they are not a cheap mailer. This page stays with void fill beside the mailers, next to board-back envelopes.
Packaging Suppliers keeps Void fill apart from a larger mailer. Loose fill and paper fill take a gap in a box. A mailer that is too big should be a smaller mailer.
What this collects
Void fill belongs beside a carton, not inside a mailer that should have been a closer bag.
board-back envelopes is the neighbour on this list. A board-back envelope keeps a document flat. It is still a different range from void fill beside the mailers.
Before the order goes in
Use fill only on the carton side of the mailroom.
TradePro at Packaging Suppliers, for trade businesses, starts at 5% off and goes up to 10% when you spend over £1,000 a month, and it adds BACS. It does not change which Void fill you needed.