6 3/4 Envelopes for Checks Our 6 3/4 Check Envelopes are made of 24# durable white paper. Charities typically mail out the #6 3/4 Check Envelope with their correspondence in hopes that they will receive a donation in return. The size of the #6 envelope, 3 5/8 x 6 1/2 is perfect for your customers when they need to mail out a personal check back to your company for payment. We will print these envelopes with all of your information including name and address as well as lines for the sender to write their return address. You will no longer have to worry about your checks going to the wrong address.
