10 x 13 Envelopes Booklet-Open Side Envelopes-Bright White 28Lb-50 per Pack-Business Envelopes (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. Comes 50 in a pack