Last year Carrera released an expanding cycle helmet which adjusts the whole helmet to fit different heads, rather than using different shells or adjustable internal straps. They have applied the same principle to a snow-sports helmet which also allows you to fold it up for ease of carriage.
This new helmet is a three-piece design with a center section and two side sections. The sides can be pulled out to change the size and fit and then lock in place. While the helmet still meets the EN1077 B standard, it would be interesting to see how big a gap there is between the sections on its largest setting. Equally, some reports state that the helmet, perhaps unsurprisingly, has good ventilation. While many skiers I know find their heads getting too warm with helmets normally and increased ventilation could be good for some, I think I’d rather retain the more limited ventilation offered by my traditional helmet rather than get a cold head. However, the folding aspect does seem appealing as a helmet which ends up 20% more compact than a traditional helmet can only be a good thing when traveling to and from resort with limited baggage.
More info from the Carerra website: http://carreraworld.com/gb/editorials/snow-foldable-helmet