Although the 3rd and 7th of a chord are the most common guide tones, other notes in various types of chords can be important in indicating the particular chord type. In triads, this can be the 5th, which can indicate a diminished or augmented chord when combined with the 3rd of the chord. In 6th chords, the 6th degree is a guide tone, as demonstrated in this example.
All the upper extensions of a chord (9ths, 11 ths and 13ths) can also be used as guide tones. The 13th degree is the same as the 6th. This means that the 7th of the chord is also necessary to distinguish a 13th chord from a 6th chord.