The five stars are as an optical macro converter. Comparison to extension tubes not considered. I have several such 2-element, achromatic converters, old Oly A-Macro and B-Macro and more recent Nikon 5T and 6T, as well as the old 3-element, +7.7 diopter, Oly A-Lifesize Macro.

This thing is awesome, great for getting started with Macro photography. The cheapest Macro lens that Olympus makes is about $500. This will get you started before you're ready to upgrade.