Lets start with letter size booklets:
The Postal Service redefined letter‐size booklets last year. New size and tabbing requirements took effect on September 8, 2009.
A booklet consists of multiple sheets or pages that are bound by saddle‐stitching, perfect binding, pressed glue or other binging method that creates a nearly uniformly thick mail piece. The requirements apply only to letter‐size booklets, not larger booklets or unbound folded self‐mailers.
The following regulations apply to all letter‐size booklets:
- Size: Maximum height = 6 inches
- Size: Maximum length = 10 ½ inches
- Paper: Minimum paper weight for cover = 40# to 80# book depending on the design
- Tabs: 3 tabs required, minimum 1 ½ inch diameter, non perforated