in Roller Game, The jam starts with the 4-member defensive team entering the track and skating in a line.
At the half-lap point, they are joined by 4 of the five members of the offensive team, who skate in a line beside them.
Once the jammer enters, the pack can spread out around the track, and skaters can engage each other anywhere at any time, and most importantly, padded body armor and gear is mandatory for player's safety and protection in the game.
Produce Japan, Ltd., a Tokyo-based company headed by Hiroshi Koizumi (小泉博), who, in 1973 at age 15 was a star skater for the original Tokyo Bombers of Roller Games.
Early star skaters included Mamoru Murakami of the Cosmos, Eiji Morita of the Lightning Jets, Takamasa Kazueda of the Delta Force, and Wataru Ueki of the Tokyo Bombers.