Tabs or wafer seals are required for direct mail letter size self mailers. There are many USPS requirements regarding tabs that can be confusing. The goal should be to design your direct mail piece to use as few tabs as possible so your mailer is easy to open and read. Design is the key not only to abide by USPS regulations but to plan ahead to use as few tabs as possible. Contact us before starting your design and we can help you with a few simple tips.
The following link describes various requirements; however, the experience of a direct mail house may better guide you to design more efficiently and cost effectively.