#20 BLENDED BALLAST - 64oz. - 1/2 Gallon. Our BEST protypical O-Scale Ballast. Great for 2-Rail O-Scale and S-Scales! Our 64oz. comes in a 1/2 gallon 'gripper jug'! #20 grade natural stone ballast accurately graded for the most discriminating protoscale modeler! Lightly blended hues for subtle contrast. Unlike other ballast, our Scenic Express stone is "sealed" so it will not darken when Matte Medium is applied. Apply with 1:4 parts Matte Medium (EX0030).