There are different ones to choose from:
Wicks with or without metal collar - Cotton wicks that can be used with most of our oil lamps. The metal collar is used to help the wick stay in the oil lamp.
Cube - A wick that comes with a metal collar and can only be used with the cube oil lamp. No other wicks will work with the cube oil lamp either.
See below so you know what wicks to get.
Wicks with & without collar - Can be used with any of the oil lamps except the Cube. Case: 10 2.6mm width, 25cm length
Cube - This can only be used with the cube oil lamp and the lamp cannot be used with any other wick. Case: 5.