I have been using these envelopes since the beginning of my business over 15 years ago. I use so many envelopes a week l that this envelopes save me a lot of time and I don't have to use my tongue to lick them that keeps my breath fresh throughout the day and my mouth isn't dry :)...I also like the security of the envelopes as well. I mail very important information in the envelopes that includes my clients important state income taxes federal taxes. I also used them to mail important papers to the Department Motor Vehicles.