The Kappa 7 was designed as a booster for Japan's later Kappa 8 and Kappa 9 rockets, as well as being used as a single-stage sounding rocket.  It was determined, however, that the vehicle was unsuitable as a single-stage rocket. The lone Kappa-7 flight was made on November 15, 1959 to confirm the motors suitability as a booster.   This is the 29mm version.  ASP also makes an 18mm version.