Couchettes for groups
Couchettes are for 4 passengers. Two seats/beds in each side. There’s only one couchette wagon, which means max capacity for 40 passengers.
No luxary, but good talk
There’s no sink, refrigirator, hanger nor table (come on, that’s not a table). But you’ll have an excellent travel by talking with old or new friends till late hours.
Cheapest way to travel alone
Couchette has one big advantage. If you travel alone, you pay for one person in couchette. And possibility to have 3 new friends is for free.