These liners are the PHP ones - they act as a one way liner keeping your baby's skin dryer and catching the poo! You get 100 in a pack. They can be flushed (one at a time) down the loo - unless you have system prone to blocking - then I would recommed popping them in bag in the bin!
We find you can wash them 2 or 3 time in with your nappie if they are only wet.
Or buy some thin fleece and make your own washable ones, though flushable liners are still good for when you are out and about.