GSM SMS standards
(These were previously determined by the European ad standards working group and apply only to messages carried over GSM mobile networks, predominant in Europe and much of the world outside the US and Asia)

• Sponsorship: A message which is up to 34 characters in length (two lines of text on most phones), designed for sponsoring content which precedes or follows the ad unit
• Full Message: A message up to 160 characters in length, typically delivered standalone.

Non-GSM SMS standards
These standards will apply to all SMS messages carried over other mobile networks, such as CDMA and TDMA, the predominant systems in the U.S.

• Sponsorship: A message which is up to 34 characters in length (two lines of text on most phones), designed for sponsoring content which precedes or follows the ad unit.

• Full Message: A message up to 100 characters in length, typically delivered standalone.