The elite medical instruments deluxe keg callipers. 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 emir keg ruler # 422 features seconds scale for pry, qtrs., cycle, length, coupling, escape, and presystolic intervals. Measures just 1 11/16 inch x 6 3/8 inch small enough to fit in a medical coat pocket.