Quality Park No. 10 Single Window Security Tinted Business Envelopes - Single Window - #10 - 4 1/8" Width x 9 1/2" Length - 24 lb - Gummed - White - Wove - 500 / Box No. 10 Single Window Security Tinted Business Envelopes offer many options for your standard mailing and shipping needs. Moisture-activated, fully gummed flap provides a secure seal. 24 lb. bright-white stock and contemporary side seams give mailings a professional look. Blue security tint keeps contents confidential while in transit.