FREE for use with an Inquisit Lab or Inquisit Web license.
The PASAT-C designed by Lejuez et al (2003) for measuring distress tolerance.
Lejuez, C. W.; Kahler, Christopher W. & Brown, Richard A. (2003). A modified computer version of the Paced Auditory Serial Addition Task (PASAT) as a laboratory-based stressor. The Behavior Therapist, Vol 26(4), 290-293.