When regenerating cartridge of an ink printer the blue tape should be pasted on the nozzle.
Correctly pasted tape preserves the ink near the nozzle from drying up and also protects the cartridge from any dirt that might get into it as a result of incorrect storing.
The cover with the blue tape on the head ( the cover is specially profiled in order to match the head in the cartridge perfectly) is another protection of nozzles from outside factors.
AGAWA.PL company advises the use of the cover whenever the cartridge is regenerated.