These rectangular porcelain palettes are great for color mixing. They are glazed on the top and sides with the bottom left unglazed. The 12 well palette measures 3-1/2" x 4-3/4" and is 1/2" in thickness. Each well measures 3/4" in dia. and are approx. 1/4" deep. The 12 well palette is available in two colors. The standard white color is generally use as a paint palette. The specially colored COBALT BLUE palette is used often in perception test. The 30 well white porcelain palette measures 5-1/4" x 7-1/4" and is 3/8" in thickness. The 30 well palette is an extremely clean, bright white porcelain. Each well measures 3/4" in dia. and are approx. 1/4" deep.