Clasp envelopes are called the because they have a metal clasp that is fastened to the envelope which keeps the envelope closed. The most common size of clasp envelopes is 9 x 12, however 10 x 13 and 6 x 9 clasp envelopes are also very common. You can mail clasp envelopes just like any other types of envelopes. We advise using a self adhesive label to print your return address or mailing address. Browse our selection of Franklin® and Statesman® style clasp envelopes below, or filter by different characteristics above.