#10 size envelopes measure 4 1/8″ x 9 1/2″ for mailing standard letter size documentsSecurity lining to maintain privacy of documentsMead all-purpose 20 lb. white envelopes are perfect for home or the office40 envelopes per boxMade in the U.S.A.SFI Certified Sourcing Product Description Each #10 envelope measures 4 1/8″ x 9 1/2″ for mailing standard letter size documents. These Mead envelopes feature a security lining to maintain privacy of documents. All-purpose 20 lb. white envelopes are perfect for home or the office. 40 envelopes per box. SFI® Certified Sourcing. From the Manufacturer Keep prying eyes off your important documents with this No. 10 security envelope with a security tint. The printed lining for privacy is ideal for sending confidential mail. Diagonal flap is fully gummed for secure seal. Each envelope is 20 lb.