When it comes to internal envelopes that get passed around frequently, you want a material that lasts. That’s where Tyvek® comes in. Tyvek® interdepartmental envelopes are engineered to provide superior durability for maximum routings and a long, cost-effective life. You can write on them and erase them multiple times without altering the look (using a pencil or erasable pen). Styles are available with resealable closures in Velcro®, Peerless Tac® or string & button. And there’s even an expansion style available.