Mikewrote a review of Giro Xen Helmet on June 17, 2011
I bought the Xen because of the extra protection in the back compared to most other xc helmets. Glad I did.
Couple weeks back I went down and broke my arm, fractured my wrist and cracked some ribs. I hit the back of my head so hard that I had amnesia. Wife says I was like 'Ten second Tom' from the movie 50 First Dates, I would reset and ask the same questions every three minutes. Did that for 12 hours. I still don't remember the crash or even going for a ride.
I'm fine now, brain is all good. Judging by my other injuries, it wouldn't be had I not been wearing this helmet. I hit the back where it offers a bit of extra protection and it cracked just like it was supposed to. Instead of my head. If you are looking for something that offers a bit more protection than the average helmet and has been tested, this one fits the bill.
On a side note it felt pretty light to me, had good air flow and my Oakley's fit well with it on.