Envelopes in DIN C6/5 combine the formats C5 and C6. At 114 millimetres, the envelopes have the width of a DIN C6 envelope and at 229 millimetres the length of DIN C5. This makes envelopes in this format ideal for sending several folded DIN A4 sheets by post. These can be invoices, offers or even contracts and other documents. For offices and companies, it is therefore always a good idea to use this "mixed form" in DIN C6/5 in addition to envelopes in DIN C5 or C6.