China overnight bullet trains now have a new category of soft sleepers referred to as "capsule sleepers". These are individual sleeping compartments.
These individual sleepers can be found on overnight D trains. On these trains, the speed has been reduced to make sure that travellers get a full night of sleep.
These are available on overnight D trains between Beijing and Shanghai, Shenzhen and Beijing, Shenzhen and Shanghai, Guangzhou and Beijing and Guangzhou and Shanghai.