6 domains, 24 facets, 1 interstitial scale
The HEXACO model adds Honesty-Humility to the familiar Big Five structure, splits Agreeableness into cooperation versus anger, and reframes Neuroticism as Emotionality. Each of the six factors has four facet-level scales (24 traits) and a 25th interstitial facet, Altruism (versus Antagonism), which cuts across Honesty-Humility, Emotionality, and Agreeableness.