Be careful, the purpose of all non certified helmets is not in any case to protect you, they are not in any case aprotection helmet.
Its only goals are:
1° to reduce the noise of the wind in freefall or in a wind tunnel.
2° to mount on it cameras and/or video cameras
3° to reduce the sensation of cold.
4° to allow you to wear galsses (for full face only)
It must not be used for the purpose of being protected from any shock.