A magnetic stripe is made up of three tracks, any combination of which may be encoded. Each track has a different encoding format.
Track One - Encoded at 210 bpi with a maximum data length of 79 alphanumeric characters.
Track Two - Encoded at 75 bpi with a maximum data length of 40 numeric digits.
Track Three - Encoded at 210 bpi with a maximum data length of 107 numeric digits.