Ultraseven 21 ("two-one") and his companion, Ultraman
Neos, were created not for a specific television series or movie, but for an
amusement park show (there was a rumor of plans for a show featuring Ultraman
Neos and Ultraseven 21, but that show has not yet materialized as of this
writing).
According to a pamphlet from the 30th Anniversary Ultraman Festival, the particulars on Ultraseven 21 are:
"Ultra Seven Two One: Height 56 m, weight 57000 tonnes. A member of the 'Space Garrison,' assigned to the 'Space Security Department.' With the ability to change his size at will, and move about at earthling size, he can change from microscopic to a height of more than 200 meters." His powers include the "Adrium Beam," the "Velzard" (the "Two One Slugger"), "Ultra X Eyes," and "Ultra Jumping."