C 6 Envelope Size Inches. Invest in a heavy cardstock and a thick envelope to protect your invitation and any. Ever since I wrote this post about string-tie envelopes I've had heaps of requests for envelope templates in standard sizes.
After you've decided on the size you require, the type or style that you need has to be decided upon.
It is based on ISO as an international standard.
How do I print an envelope that is not a standard size as set in the printer. Our envelopes come in many shapes and sizes, plain or with custom printing and in the largest selection of colors. Series C is primarily used for envelopes.