The is a commuter EMU

Multiple unit

The term multiple unit or MU is used to describe a self-propelled carriages capable of coupling with other units of the same or similar type and still being controlled from one driving cab. The term is commonly used to denote passenger trainsets consisting of more than one carriage...

 train type operated by Seibu Railway

Seibu Railway

is a conglomerate based in Tokorozawa, Japan, with principal business areas in railways, tourism and real estate. Seibu Railway's operations are concentrated in northwest Tokyo and Saitama Prefecture; the name "Seibu" is an abbreviation of "west Musashi," referring to the historic name for this area...

 in Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

. It is nicknamed the "Smile Train".
A total of 120 4-door vehicles (formed as 18 sets) are on order to be delivered between fiscal 2007 and 2011, replacing older 3-door 101 series and 301 series sets. Three 8-car sets were scheduled to be delivered in January 2008, with subsequent deliveries consisting of nine 8-car sets, three 6-car sets, and three 2-car sets. The trains feature aluminium wide-bodied (2,930 mm) 20 m long cars with no end gangway doors.

The first trains entered service on the Seibu Shinjuku Line in April 2008.