What size envelope should be used to mail a standard size business letter? The most common type of business envelope is the regular envelope. A popular #10 envelope measuring 4 1/8" by 9 1/2" is ...

The W+D BB820+ will handle all direct mail envelopes sizes from a #7 (3¾ x 6¾“) envelope now up to a 10 x 13” flat with a package thickness of up to 6/₁₀”.

Domestic Priority Express Mail Flat Rate Envelopes: $30.45: Please note: Letter rates are only for normal business envelopes (sizes #6 or #10), which are no larger than 6-1/8" in height and 11.5" in ...