Airbag-helmet and airbag adapted for being used as a part of such an airbag-helmet

An airbag-helmet comprising:

• a protective main body having an inner surface facing towards a head of the user when the airbag-helmet is worn, and an outer surface facing away from the head of the user when the airbag-helmet is worn;
• a cover attached to the outer surface of the main body;
• an inflator;
• and
• a single airbag attached to the protective main body at least indirectly and being in fluid communication with the inflator, said single airbag comprising at least three tubular protection sections forming a T-shape, each of the at least three tubular protection sections extending along the outer surface of the protective main body when the single airbag is in an un-deployed state and when the single airbag is in a deployed state, wherein in the deployed state, the single airbag is filled with gas by the inflator and extends from the outer surface of the protective main body;
• wherein at least one of the protective main body and the cover has a groove formed between the cover and the outer surface of the protective main body, the groove having a continuous bottommost surface located between the cover and the inner surface of the protective main body, wherein an entirety of the single airbag is located inside the groove between the protective main body and the cover when the single airbag is in the un-deployed state.