Combine our Rapid ID - Intervals and Measures with the pocket EKG ruler for all your EKG tracing needs. Measure EKG intervals, heart rates and QRS complex segments with this combo pack that contains a quick and easy way to measure heart rates down to 20 beats/minute and heart rate pauses to 3 seconds on full 12-lead EKGs or rhythm strips. Standard reference ranges are provided for the P Wave, PR Interval, QTC Interval, ST Segment, and QRS Complex. The EKG ruler provides even more references for axis determination with detailed QRS segment normal values and locations.