The paper rolls for the SAM4s SPS-520FT or 520RT are the 2.25" thermal
The SPS-520 series (RT and FT) have both a receipt and journal printer on board. Both side use the same paper and of course because they are thermal there is not need for an ink ribbon. The paper is also very easy to change. Make sure you close the printer after changing the paper, failure to do so will result in a cover open error. Make certain to keep paper in both sides even if you don't issue a receipt with every transaction.