The tightening / loosening action involves a three-finger grip in which the thumb is positioned to the side, while the phalanx on the middle finger opposes the index finger.
The role of counterposing the middle finger to the thumb is reinforced by the support that the third finger gets from the fourth and fifth fingers.
The three different head diameters provide for increasing the complexity of the task. The entire support is made of anti-bacterial polyethylene that is water and UV ray resistant and easy to sterilise.
It has 3 head diameters for varying levels of difficulty in gripping for the hand - wrist. The “heads”, made of polyethylene like the support, can simulate the caps on food jars, a light bulb, gas tap, etc.