Thanks to Digi-Flex's spring-reinforced buttons for each finger, weak fingers do not prevent strong fingers from working. This feature allows you to have an easier, faster and more successful rehabilitation process. 5 different resistor/color products are available. Having different resistance measures allows therapists to measure progress. Resistors Yellow / 0.7kg Red / 1.4kg Green / 2.3kg Blue / 3.2kg Black / 4.1kg