1. 7-Step ECG Ruler: A clear ID-sized card that makes interpreting an ECG easy. Perfect for anyone with an ECG/EKG practice from a student to an experienced physician. 2. Size: Perfect size to fit in your ID holder for easy storage and access, designed for the 7-step ECG interpretation . 3. Follow the 7-step plan and reference those hard to remember key points! 4. Axis: Quick reference to deviation from normal, left axis, or right axis. An upward arrow indicates a positive deviation and a downward arrow indicates a negative deviation. Please note: the physical slightly color difference or difference, does not affect the use, please do not mind, thank you! Color: As shown Material: plastic Package Contents: 2 x 7-Step ECG Ruler Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.