It could be the most important piece of gear you ever buy so choose right - you'll have a lifesaver.
If you're into one adventure sport then chances are you'll be open to others. A kayaking buddy might offer to take you paddling while a climber friend might threaten to introduce you to their favourite route.
But with each new sport comes another pounding to the bank account for all the gear that goes with it, and despite the risk of a similar pounding to your skull, there's a strong temptation to forgo a new helmet each time.
Thankfully there are a few multi-sport helmets that will cover you for more than one activity, but it's a compromise to balance lightness, protection, temperature control and ergonomics. But make the right choice, and you'll have something that will protect your dome whether you're climbing or riding the half pipe.
POC Receptor + stands out among the crowd as the only one we could find that is certified for snow, wheels and water. It's built like a wrecking ball so a little heavy for cycling. The protection uses a layer of Aramid (a form of Kevlar), and an outer shell which takes care of the little knocks and bumps but doesn't react to sticker adhesive, so you can personalise it without affecting the protection.
Like fellow Swedes at IKEA, POC have taken a self-assembly approach to the helmet with an insulation insert that blocks the ventilation to keep you warm on the chair lift, but can be removed to keep you cool during telemark climbs. A removable padded neck roll keeps your ears out of the wind, and POC also do an optional version with built-in speakers and microphone that connects to your phone.
The understated crash-test-dummy graphics are undeniably cool, and the chin strap is as reassuringly snug as a pair of 1980s Y-fronts, all of which goes to make this a piece of gear you'll love using when you're pushing the envelope.
Certified for: skiing, snowboarding, bikes, skateboard, roller blades, kayaking. www.pocsports.com
Petzl Mentor III This featherweight lid is rated for climbing, cycling and white-water, and at just 235grams you can afford to add to your pack for any adventure. With more holes than a Swiss cheese, it's well ventilated. Petzl have also included four head-torch mounts so you can use one of their lamps to climb through the night or alternatively mount your GoPro in any orientation.
Certified for: climbing, cycling, whitewater
Salewa's Xenon helmet is also worth looking at. It's good for snow, wheels, sledging, as well as alpine climbing and ski mountaineering. But adventure racers will be disappointed that kayaking is not also covered. The 10 vent openings ensure your head stays cool in summer. It comes with insulation inserts for winter. When the weather turns cold all you have to do is remember where you put them.
Certified for: Snow Sports, Cycling, Skateboard, Rollerblades and Sledging