Professional watercolorists around the world choose watercolors from Daler-Rowney for perfect washes of pure free-flowing color, with no hard edges. Each color is individually formulated, using only the finest pigments — whatever the cost — and milled up to nine times through traditional granite rollers to retain the purity of the color. Each batch of color is checked for tint and texture against samples going back over ten years. In addition, colors are subjected to accelerated heating and freezing to ensure color stability, even in the most extreme conditions. Studio size tubes are 15 ml (.51 oz).