Roor Standard Bowls these are your standard Roor bowls, they all need a glass screen to work properly. You have a choice of bowl size with these. Your Roor bong will have come with a medium bowl. The two other sizes available to you know are Small and Large. This relates purely to the bowl size with small being a popular upgrade. Roor bowls are the perfect addition to any roor bong. Using the same premium schott duran glass the artisans at roor deliver the perfect bowls for the perfect glass bongs. By choosing a roor bowl, you are ensuring that your smoking experience is exactly as the owner and chief designer Martin Birzle wanted you to have.