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Everything you need to know about envelopes

C sizes

'C' series sizes refer exclusively to envelopes, as opposed to 'A' sizes which refer to paper and 'B' sizes that cover paper and some envelopes. Other common envelope sizes are under size DL, oversize DL and oversize C5. These oversized envelopes are particularly suitable for use with automatic mailing machines which insert contents mechanically. (See also ISO paper sizes).