Quality Park 24524 Quality Park Security Tint Double Window Invoice Envelopes, 9, White, 500/Box Envelope is security tinted and includes a bottom left window (3 1/2w x 1 1/4h) plus a top left window (4w x 1h). Double window shows mailing and return address. Wove finish. Blue security tint. White window envelope features a gummed closure White window envelope features a gummed closure. Envelope is security tinted and includes a bottom left window (3 1/2w x 1 1/4h) plus a top left window (4w x 1h). Wove finish. Blue security tint. Double window shows mailing and return address.