What do you need to know? Schedule, route or specifics about the trainsets?

On the timetables, they're the "D" trains. One in English is http://www.travelchinaguide.com/china-trains/

Very frequent on eastern China routes like Shanghai-Hangzhou (fastest - 1:18) and Shanghai - Nanjing (2:03).

Examples in northern part of the country, Beijing - Tianjin (1:09).

In the south, Guangzhou - Shenzhen (0:52).