Every helmet must meet one requirement: It must fit properly. This is the only way it can offer you the necessary protection in the event of a crash. But there is no such thing as the one perfect MTB helmet. For this, the disciplines within the MTB riding are simply too different and the requirements of the individual too different. In addition, a helmet always represents a compromise from several aspects. A Downhill full face helmet can provide massive protection, but it will never be incredibly light and airy. In contrast, a half-shell is much more comfortable to wear in all-day use, even at high temperatures, but will never be able to offer the same protection as a full face helmet.