What are security tint envelopes?

Security tint envelopes are designed for sending sensitive information through the mail. They are most often used for financial documents, personal information like medical records, checks, government correspondence and anything else the sender or receiver wants to protect from unwanted viewing. Common sizes for these are: # 10 in both regular and window. # 9 in both regular and window. # 6/34 Simple Seal #10 with Security Tint.