Blue Summit #10 Pistol Window Envelopes with Gummed Seal, 4-1/8” x 9-1/2” Blank Envelopes, 500/BoxPerfect for mailing invoices, billing statements, checks, and other business mailings. Strong gummed adhesive with 1 tapered flap creates an easy and safe closure for all sensitive documents. Single pistol window envelope will show the mail recipients address through the window. #10 envelopes can hold #9 or #8 return envelopes to help get your invoice paid faster. 500 envelopes per box Save time and money by sending business mail with our #10 single