No. 10 White All Purpose Window Envelopes with Wesco Black Inside Security Tint, 4-1/8″ x 9-1/2″. No. 10 White All Purpose Window Envelopes with Wesco Black Inside Security Tint, 4-1/8″ x 9-1/2″, White Sulphite 24-lb (SFI Certified) with Vellum Finish – Box of 500 Envelopes.