Lob Help Center

Mail piece design specs

Available form factors and their design specs

Lob offers a variety of form factors and related features that is accessible via the API or dashboard. 

Postcards & self-mailers

  • 4x6" postcards
  • 6x9" postcards
  • 6x11" postcards

  • 6x18" bifold self-mailers
  • 12x9" bifold self-mailers
  • 11x9" bifold self-mailers


  • 8.5x11" letters
  • Using Certified Mail & electronic return receipts
  • Using Registered Mail
  • Using card affix

Letter envelopes

  • Standard outer envelopes (#10 and flat envelopes)
  • Certified Mail envelopes (#10 envelopes)
  • Return envelopes & tracking (#9 standard envelopes)
  • Business reply envelopes (#9 standard envelopes)
  • Custom outer envelopes (#10 envelopes)


  • Adding a bank account
  • Adding a signature
  • Adding check pages

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