9 x 12 White First Class Envelopes, Open-End Flat, Peel & Stick, White Wove, 500/Box These 9 x 12 white first class envelopes are made of a crisp 28# white wove stock with a perfect balance of quality and economy. They are 9" x 12" with the opening on the 9" side. These envelopes are pre-printed with standard First Class Mail" markings including a green diamond border." They feature a peel and stick closure for easy mailing. They are priced and shipped per box of 500.