This version of the Big Five personality traits administers measures from the International Personality Item Pool.
The five scales used are: extraversion, agreeableness, conscientiousness, emotional stability and intellect/imagination. These were developed to measure the Big-Five factor markers reported in the following article: Goldberg, L. R. (1992). The development of markers for the Big-Five factor structure. Psychological Assessment, 4, 26-42.