1.The extension tube moves the lens farther from the film or digital sensor. The farther away the lens is, the closer the focus, the greater the magnification.

2.This extension tube does not affect image quality as there is no optics inside. In comparison, a close up filters are often blamed for degrading image quality.

3.Camera Body Mount Adapter
Lens Mount Adapter
9mm tube (Tube 1)
16mm tube (Tube 2)
30mm tube (Tube 3)

 The more tubes you add, the closer the focus and the greater the magnification.

Extention Tube: