10 x 13 Large Booklet Envelopes-Open SideEnvelopes-28Lb White Big Envelopes 500 Box (500/Box 10x13) 10x13 Booklet white Multi-purpose envelopes These are standard 28 lb white stock Has Moisture activated gummed seal. Great for mailing out sales brochures, annual reports, and product literature Check O Matic 100% Satisfaction Guaranteed. 500/Box