Unbreakable ruler is made of a unique material that s durable enough for even the messiest classrooms but is still light and flexible enough for even the youngest students to use. Transparent construction makes it easy to see what you are measuring for accurate use. Easy-to-read numbers in both Imperial and Metric graduations help prevent reading errors for precise measurements. Hang hole offers a convenient way to keep this ruler within easy reach. Helix Unbreakable Ruler Clear 10 / Box (Quantity).