On the left is CD 166[010] with the "A011 / CALIFORNIA" embossing. The A011 is typically very weakly embossed to the point of being nearly invisible. This one is a purple/peach 2-tone. This heavier duty model has a squarish dome and a skirt that flares out. In all respects this is one chunky signal insulator that comes in a wide range of colors & 2-tones. On the right is CD 166[020] with just the " CALIFORNIA " embossing. This is the "slim fast" mold type with the round dome and "straight sides" skirt which is noticeably thinner than [010]. This one comes only in blue, blue aqua, green, green aqua and aqua. For more information contact me or read Brent Burger's informative series of articles on the California insulator published in Crown Jewels in the early 1980's.