The Elite Medical Instruments Deluxe EKG Calipers. The tool for accurately measuring electrocardiogram wave sections. Made with hardened steel and includes plastic protective cover for easy reference. Comes with reusable pvc pouch carrying case. Includes the EMI EKG Ruler # 422 features seconds scale for PR, QRS, Cycle, Length, Coupling, Escape, and Parasystolic Intervals. Measures just 1 11/16 inch x 6 3/8 inch small enough to fit in a medical coat pocket.