Using your finger, move the measurement head through flexion, extension and hyperextension. Measures 110? flexion and 40? hyperextension in 5? increments. Arm has 10cm/4" scale. This goniometer is also known as a one hand goniometer because the therapist using only one hand can take readings and can use the other hand to stabilise the patient or record the measurements. The standard finger goniometer requires the therapist to use two hands to make a finger range-of-motion measurement.