Made from long-fiber Kraft paper, Roptex envelopes are much more durable than regular Sulphite 24 lbs stock paper. These envelopes are primarily used to send contents that are too heavy to be sent in regular paper envelopes. This 6 3/4 envelope is made from brown Kraft paper and has a vellum finish. These envelopes come with a regular moisture-activated sealing system that’s quick and easy to use. The envelopes have a classic styling with diagonal seams and a simple flap-down design. Thanks to its enhanced durability, these envelopes are perfect for sending overseas mails as well as heavier items. These 6 3/4 envelopes are also often used as return envelopes when slipped into any larger size envelope.