With this acrylic ruler's convenient 5 x 5 mm grid, you will always know if your lines are truly parallel. On one side of the ruler, the "zero" measurement starts at the edge of the ruler, so you can easily align the "zero" mark with the edge of what you are measuring. This is convenient for measuring heights and depths, where an extra gap between the "zero" mark and the edge of the ruler may get in the way. Another feature that helps in measuring heights is vertically printed numbers on the side where "zero" begins. This makes them easier to read when the ruler is held vertically. On that same side, measurement markings go up to 16 cm, while on the other side, they go up to 15 cm. Every 5 cm, the measurement is outlined with a dark circle, making it easier to quickly read the measurement. You can enjoy your ruler for a long time because of its high-quality clear acrylic that's durable and attractive at the same time!