Like the 400 Series Shinkansen these trains are built to a smaller loading gauge to fit on the narrower clearances of the 'mini-Shinkansen'.
The initial units built starting in 1997 were 5-car sets, but sixth cars were built to integrate into the existing units by the end of 1998. Production is ongoing, with 25 sets scheduled to be produced ending in 2005. Two sets have a seventh car.