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  • Giro Aeon Helmet
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GiroAeon Helmet

Temporarily Out Of Stock

Item # GIR0402

Don't get too bummed. This item is on the way and will be available for purchase as soon as it rolls into the warehouse.

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Fit should never be in flux.

Giro’s ultralight helmet, the aptly named Prolight, weighs in at 22 grams less than the Aeon you see here. What do those 22 grams get you? A more adjustable helmet. The Aeon includes Giro’s Roc Loc 5 adjustment around the circumference of your head, as well as strap buckles beneath your ears, neither of which you’ll find on the Prolight. If you never wear a cap or winter hat, and the Prolight fits just fine, then you’re 22 grams ahead — for the rest of us, there’s the Aeon.

  • Roc Loc 5 adjustment system
  • SL Roll Cage maintains helmet’s integrity in the event of a crash
  • 24 Wind Tunnel vents move air in, through, and out of the helmet
Tech SpecsSize
Tech Specs
This product can expose you to chemicals including Bisphenol A (BPA), which is known to the State of California to cause birth defects or other reproductive harm. For more information go to
Shell Material
24 Wind Tunnel vents
Fit Adjustment
Roc Loc 5
Recommended Use
cross-country, road cycling
Manufacturer Warranty
1 year


Adult Cycling Helmets
Super Fit™
Head Circumference

18.5 - 20in

(47 - 51cm)

20 - 21.75in

(51 - 55cm)

21.75 - 23.25in

(55 - 59cm)

23.25 - 24.75in

(59 - 63cm)

24 - 25.55in

(61 - 65cm)

Head Circumference

21.25 - 24in

(54 - 61cm)

19.75 - 22.5in

(50 - 57cm)

22.75 - 25.5in

(58 - 65cm)

How to Measure:
For best results, use a tape measure to measure around your head where your hat would fit comfortably.

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Giro Quality

  • Familiarity: I've put it through the wringer

Great fit, lightweight, breathable...all things that you can expect from this helmet to be honest.
The Giro fit quality is great, I owned another Giro and I knew that just buying the same size will fit, that gives you a lot of confidence when buying.
This helmet is also very light and breathable, which helps when riding in the middle of summer in hot and humid Costa Rica!

Is the Aeon more oval shaped than the Synthe?

as far as fit, interior shape of the helmet, they are pretty similar in fit, they feel the same to me.

I have found the new Giro helmets DO NOT fit the same as the older ones like the Atmos and Aeon. The newer ones are definitely smaller. For example, Im a perfect small in an Atmos, with room to spare, but when I tried on the Aether, it would not even go on my head. The Synthe fits me, but once I put a cap under it or a balaclava, it no longer does.

Great Fit

  • Familiarity: I've put it through the wringer
  • Fit: True to size
  • Size Bought: M

I always seem to be going back to Giro helmets since their retention system and overall fit suits my head the best. Competitive Cyclist also somehow figured out a way to get it delivered during Thanksgiving Day,which was a pleasant surprise....

will the large size accommodate a 7 7/78 head? I usually need an XL helmet...

Probably. I wear a 7&3/4 baseball cap, and usually wear a Large helmet, but the Medium Aeon actually fits me - so I imagine that the Large Aeon will fit your size (shape, of course, is another factor…)

Perfect fit

  • Familiarity: I've used it several times
  • Fit: True to size
  • Size Bought: Large

I have worn several helmets and this is by far the best fit I ever had. Easy to adjust. The numerous vents provide great ventilation which is a major plus for me because I am not tolerant of heat. Price seemed fairly priced compared to other helmet's I researched. For me the Giro Aeon is a perfect fit.

Very good helmet !

  • Familiarity: I've used it several times
  • Size Bought: Large

Very well made , light and confortable. No complains so far . This is my 3 giró helmet and no regrets .

Giro saved me

  • Fit: True to size
  • Size Bought: Large

Aeon saved my life .Crashed at 30 mph with primary landing on Giro .
Helmet showed minor internal cracks as it should.I walked away with
body bruses and minor concussion .Purchasting another.
Yury G

I love Aeon over Synthe

  • Familiarity: I've used it once or twice and have initial impressions

I am going to buck the trend of unlimited praise for the Synthe and vote for the Aeon. I mean, of course the Synthe is a nice helmet and it has MIPS. But I got both it and the Aeon and ended up preferring and Aeon for a couple reasons. First, the fit of the Synthe is not as good for me--and fit in a helmet of this quality is enormously important. I did not find the adjustments worked for my head, which is large and not as round as the Synthe shape. The only way I could get a good fit was to tighten the Synthe to the point of unpleasant pressure. The Aeon, by contrast, is more the traditional Giro shape, a little longer fore-to-aft and narrower side-to-side. The second aspect is what my wife spotted as soon as she saw me with the helmets on-the Aeon looks better. The Synthe is round, sits very high, and is more like wearing a mushroom. The Aeon, again in the traditional style of Giro, is less round, sits closer to the head, and looks, well....faster! As for MIPS, to my mind, the jury is still out on its actual value and how to best implement the concept. In the meantime, my new Aeon is comfy, insanely light, and beautiful.

Aeon helmet

  • Familiarity: I've put it through the wringer
  • Fit: True to size
  • Size Bought: Small

Really light . fits great !!! And great price!!! Also pretty cool in dead of summer if your moving its great .

A Helmet that Fits Like a Glove

  • Familiarity: I've used it several times
  • Fit: True to size

No need to acquit, this helmet fits! Let me say from the out outset - I have a Giro shaped head. I have not found a helmet brand, other than Lazer, that fits my head so well. I have purchased, used and been happy with Speciaized, and POC, but now that I have another Giro I am asking myself why I ever left. As far as use goes, strap adjustment was a very easy, and I set it up in minutes. The fit works very well with my Smith glasses. The airflow is great, and I am very pleased with the finish, function, and fit. At this point I am very happy with it.

I agree with you--the fit on the Giro is consistent and works for me. I have a Laser too, the only other helmet that was close, but it is still not as comfy as the Giro and I, too, have returned to the fold. Be careful of the Synthe, which has a different fit and overall shape.

Love it

  • Familiarity: I've used it once or twice and have initial impressions

Very lightweight, breathable, and comfortable. I tried this and the Atmos while shopping for a new helmet. Both are awesome... the Aeon just seemed to fit my melon better. It also looks great and I can ride confidently knowing that, if I ever unintentionally come off the bike, my skull has an extra layer of protection.

my favorite helmet

  • Familiarity: I've put it through the wringer
  • Fit: True to size

fits like a champ, lots of wind flow

Are the helmet straps removable (i.e. removable for washing)?

I have the 2013 model, well had, which appears identical and they were not. I just ran under water when the salt stains got too bad.

No straps are not removable on giro's but you can just wash the helmet off in the shower and hang it up to dry. You can remove the pads and wash separately.

Covers Your Noggin While You Tri Harder

This helmet is very light, which helps me maximize efficiency during a race. Pictured above making the turn before plunging downhill.

Covers Your Noggin While You Tri Harder

Great lightweight helmet

  • Familiarity: I've used it several times

Just what I was looking for, lightweight and brightly colored for early morning bike rides. Love it!!

High Vis Brah

  • Fit: True to size
  • Size Bought: Med.

Yes, it’s light weight and breathable, but more importantly its thermoformed skeleton inside the EPS foam is what keeps my noggin safe. I have used it on the road and on the trail when I need the extra ventilation. Standard fit and I dig the High Vis.

Great Helmet

  • Familiarity: I've put it through the wringer
  • Fit: True to size

This is truly a lightweight helmet. Its very comfortable and I quickly forget that it is even on. The venting is excellent (summers are hot and humid here). The straps are narrow and not as rough as my previous helmets (including the old Ionos model). The Roc Loc system adjusts easily and is effective at holding the helmet in place. The only bad thing I can say about the helmet is that it is overpriced. But so is most cycling gear.

lightweight and comfortable

  • Familiarity: I've put it through the wringer
  • Fit: True to size
  • Size Bought: medium

Rode this helmet in the heat of the summer. Great fit, lightweight and nice adjustments.

On the road again...

  • Familiarity: I've put it through the wringer

I've put this helmet through the wringer with Leadville and training for the event. My wife liked the bright color so she could see me from the feedzone. It fits as expected of a GIRO product, pressure points match up to my other Giro's through the years, so no issues with fit or sizing.

Survived a hard crash at 25mph

  • Familiarity: I've put it through the wringer

Crashed at 25mph in HH100 this weekend. Landed on my head and shoulder. My immediate thought was no way I 'm not concussed. But after walking around and going thru some mental drills (3 prior concussions so I know the signs) I continued riding. The Aeon structure cracked and split on one of the ribs, but protected me from head damage. It's very light and airy. Not a perfect fit, but workable. I'll retire it now.

Similar accident last weekend with a similar outcome. Just ordered a like replacement.
HH100 is a buster!!