"WIN350" was the name given to the 6-car experimental high-speed Shinkansen train developed in 1992 by the West Japan Railway Company (JR West) in Japan to test technology to be incorporated in next-generation shinkansen trains expected to operate at speeds of from 1994. Initially given the designation "500X", the name "WIN350" stood for "West Japan's Innovation for operation at 350 km/h".
Cars 500-901 to 500-903 were built by Kawasaki Heavy Industries in Hyogo Prefecture. Cars 500-904 to 500-906 were built by Hitachi in Yamaguchi Prefecture.
The front-end designs of the two driving vehicles (500-901 and 500-906) were slightly different, with 500-906 featuring a "cockpit" style arrangement. The external livery was purple and light grey, with darker purple lining.
All axles were motored, using 300 kW three-phase motors, and cars were equipped with tilting and active suspension.
Internally, only car 4 was fitted with passenger seats, with 10 rows of 3+2 standard-class seating and 5 rows of 2+2 Green class (first class) seating.
The 6-car set, designated "W0", was formed as follows.
Initially, cars 1, 2, and 5 were fitted with pantographs.
The WIN350 train was delivered to Hakata Shinkansen Depot in April 1992.
On 6 August 1992, the train recorded a Japanese national speed record of on the San'yà  Shinkansen. Two days later, on 8 August 1992, the train recorded a Japanese national speed record of on the San'yà  Shinkansen between Ogà Âri (now Shin-Yamaguchi) and Shin-Shimonoseki.
The WIN350 trainset was withdrawn on 31 May 1996, and a special farewell ceremony was held at Hakata Shinkansen Depot.
End car 500-901 is preserved outdoors at the RTRI large-scale wind tunnel test facility in Maibara, Shiga. Initially expected to be moved to the Modern Transportation Museum in Osaka, end car 500-906 was stored at Hakata Shinkansen Depot until being scrapped in May 2024.