Elastic tube made of silicone rubber with inner diameter of 2 millimetres is often used to transfer liquids. Comparing to the natural rubber, silicone rubber is less elastic, but it is more resistant to chemicals, heat and UV light (sunlight). This specific tube with 2-mm inner diameter can also be used as a friction wheel on the 2-mm shaft of DC motors to transfer the movement to other wheels or surfaces.
It can also work as a short distance coupling for 2-mm shafts of small DC motors, generators, propellers and similar components.