Abstract: It is a typical harness conformed by a hard outer shell (1) that usually projects a front visor (2), and an optional crown with ventilation ports (3), enclosed in an inner harness (A) that lays on the wearer's head, keeping a considerable clearance in respect of the inner face of the shell (1). The helmet is put on the wearer's head and is positioned using an adjustable annular headband (4). The harness is a crowned thin structure conformed by curved portions of different width and equal thickness, which form stretching deformation portions based on the energy transferred during an impact. Thanks to the sizing of the curved portions that form the crowned structure, stretching deformation occurs at temperatures ranging from ?18° C. to 50° C. The crowned structure is shaped from an upper elliptic portion (5) that delimits a vast upper and central opening (6) that is substantially elliptic, from which radial portions extend (7 and 8) until reaching a lower adjustable annular headband.