#9 Double Window Envelopes for Quickbooks Checks - Security Self-Seal (CP31-603-SS)Overview Speed up mail runs with self seal window envelopes in the compact No. 9 size. These double window self seal envelopes keep address info visible and amounts hidden thanks to a privacy tint and comes with 1000 envelopes. Make mailing easy with envelopes for QuickBooks checks. Our QuickBooks compatible envelopes keep addresses aligned and amounts hidden, so your documents look professional. Choose window envelopes for QuickBooks checks in