Just Jump offers multiple test modes for testing not only vertical jump height to an accuracy of 1/10th of an inch, but other performance factors. Simply stand on the mat with your feet together and jump, and the system calculates your vertical jump height by measuring the time that your feet are not in contact with the mat. The hand-held, battery-operated unit displays maximum height attained and "hang time" for one jump. It also calculates average height plus ground time for four jumps, computes explosive leg power, and can compute foot quickness (shuttle runs and dashes). Records up to 60 jumps.The Just Jump vertical jump tester consists of a square jumping pad (28") and a hand-held, battery-powered computer unit. Hand-held, computerized digital display. Operates on a single 9-volt battery so it can be used anywhere. Records up to 60 jumps, and calculates average height, contact times, and leg power for the first and last 15 jumps.