Macro extension tubes are sold alone or in a set of two or three pieces. It can be used separately or sorted together to adjust the length. The longer it gets, the closer it can be to the target.
Below are the recommended length when using soratama. This is according to our tests with 35-50mm of focal distance (35mm equivalent focal length)
The length changes depending on the sensor size and lenses.
MICRO FOUR THIRDS 10mm
Full size 32mm