Well basically it is a drink package that includes unlimited beer, wine or soft drinks at lunch and dinner. For our 7 day Med. Cruise it was $99 USD per adult. It really is a great deal. You can take partially consumed bottles back to your cabin with you, so frequently at night we would drink a bottle of wine. They would uncork another and we would drink a little out of it and take the remaining opened bottle with us. So we had a nice collection of wine in the cabin. We really enjoyed the red wines we had, the blush were good, the whites were so so.
I ordered it through my Travel Agent. She was not familiar with the X-1 so she simply called Costa and was able to order it easily.