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  • Matte Black, M ($199.95)
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Item # GIR0402

Cooling comfort.

In the never-ending quest for helmet lightness, one fact makes us rest easy: Even the most feathery helmets must pass the CPSC safety standard for impact resistance. If, for example, you've ever picked up a Giro Prolight or Aeon helmets, you know why this is a concern. It seems impossible that a near-weightless thing like these helmets offers adequate protection. Amazingly, though, they pass the CPSC testing just fine.

The Prolight tips the scale at 200 grams, nearly 50% lighter than most alternatives in its $200 price range. Its lightness comes thanks to several factors, the most noticeable of which is its lack of fit adjustment hardware. Its Roc Loc SL is made from elastic and offers none of the fine-tuning of other Roc Loc models. Furthermore, the strap buckles beneath your ears are fixed and non-adjustable on the Prolight. And while this might seem like a reasonable price to pay for lightness, if you ever choose to wear a cycling cap or winter hat beneath your helmet, the resulting tightness around your head is a bummer.

Enter the Giro Aeon. With the Aeon, Giro's goal is to offer the next generation of superlight helmet design. The Aeon marries the breathtaking lightness of the Prolight and the fabulous ventilation and adjustability of the Ionos.

At 218 grams (size Medium), the Aeon is in the same weight class as the Prolight, but it offers far more fine-tunability to the fit. It comes with Giro's all-new Roc Loc 5 retention system. For starters, the indexed Micro Dial lets you adjust the tension with a two fingered twist. And itsGiro Aeon Helmet  Detail three position bracket allows 15mm of vertical adjustment in the retention basket -- enough to fit any head shape comfortably. In another improvement over the Prolight, you get clever strap management. The retention basket has strap holders to ensure that they'll be right where you want them by the time the helmet falls into place on your head.

The Aeon uses in-mold construction to fuse the foam liner to the abrasion and puncture resistant polycarbonate shell as other Giro helmets. However, Giro uses a low-density EPS liner for the Aeon that performs the same important task of absorbing impacts, yet it's 15% lighter than the foam they used previously. Giro took advantage of that weight savings by foregoing the composite reinforcement found on the Ionos. Instead, a thermo-formed SL Roll Cage reinforces the Aeon for maximum safety, yet it's 49% lighter than the Ionos' composite sub frame.

The Giro Aeon Helmet has 24 massive Wind Tunnel vents to suck cool air in the front and flush warm air out the back, even at relatively slow speeds. The Giro Aeon is available in the sizes Small, Medium, and Large and in the colors Highlight Yellow/black, Matte Black, Matte Black/white, Matte Black/color fade, Matte Black/yellow Livestrong, Matte Blue/black texture, Matte Red/black, Matte Titanium, and Matte White/silver.

  • 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 Specs

Impact Foam:
Thermoformed SL Roll Cage
24 vents
Fit Adjustment:
adjustable chin strap, Roc Loc 5
Claimed Weight:
222 g
Recommended Use:
road cycling
Manufacturer Warranty:
1 year

Size chart


Adult Cycling Helmets
 SS/MMM/LLXLAdult UniversalWomen's Universal
Head Circumference 20 - 21.75in
(51 - 55cm)
20 - 22.5in
(51 - 57cm)
21.75 - 23.25in
(55 - 59cm)
21.75 - 24in
(55 - 61cm)
23.25 - 24.75in
(59 - 63cm)
24 - 25.55in
(61 - 65cm)
21.25 - 24in
(54 - 61cm)
19.75 - 22.5in
(50 - 57cm)
Head Circumference 20 - 20.75in
(51 - 53cm)
21.25 - 22in
(54 - 56cm)
22.5 - 23.25in
(57 - 59cm)
23.5 - 24.25in
(60 - 62cm)
How to Measure:
For best results, use a tape measure to measure around your head where your hat would fit comfortably.

Reviews & Community


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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.

Avg. ride time: 9h 11m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

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.

Avg. ride time: 9m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

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.

Light + cool + love

  • Familiarity: I've put it through the wringer

When I first started cycling somewhat regularly, I balked at buying much more than the most basic helmet, as I didn't understand the value in having a very lightweight, well ventilated helmet. After a few thousand miles in the saddle, I got the joke and picked up the Aeon. The Giro helmets all fit my head shape quite well, and when I wear the Aeon, I feel like it is almost not even there. A top quality helmet is a worthy upgrade for anyone who puts in decent mileage on his or her machine.

Photo: telling my friend Brett to put his bike down (raising it over one's head is a serious roadie rule violation!) after a big ride through CT, NY, and MA. Sharon, CT

Light + cool + love

light and stylish

  • Familiarity: I've put it through the wringer

The Aeon is my favorite Giro helmet. Its very light and breathes better than any of my other lids. I love the way it looks and I've never had an issue with the RocLoc. Tons of color options is nice too!

Avg. ride time: 9h 58m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

super lightweight and breathable

  • Familiarity: I've put it through the wringer

Not really a fan of the latest helmet designs and styles so I hope that Giro will continue to produce this helmet for a long time. I have ridden this on 100F+ days in georgia and down into the 20's wearing this... No complaints. It is so lightweight that I have had to check with my hands a couple of times on cold days to make sure I had my helmet on...

Avg. ride time: 28m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

What's with all the stars?

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

I see a LOT of road cyclists with this helmet so I thought I'd give it a shot. Don't see what all the hype is about. Looks okay but not great (I tried the black). Maybe one of the colored ones would look nice if it matched your kit. But in terms of breathability the mavic plasma or the catlike mixino both breathe better (hence only 3 stars). In terms of comfort I had no complaints.

Interesting that mishkin can comment on the helmet's breathability, having returned it prior to use.

ha! Bill, I used the helmet a couple times before deciding it wasn't for me. That was so long ago that it almost seems moot now. After the catlike and the mavic, I am now riding a giro synthe as my main helmet and it is great and just as breatheable as either of those.

The best for a reason

  • Familiarity: I've put it through the wringer

I ordered a POC Octal to be quirky/cool/different and match my two Cervelos. I couldn't get over the mushroom vibe no matter how light it was so I returned it for the Giro Aeon. Also toiled over the Catlike, but couldn't be happier I went Giro.

I got it in fluorescent orange to stick with the high-viz theme and it definitely passes the test. Bright, light, most comfortable helmet I've ever owned.

It gets breeze to my scalp through my mop of hair and has no compatibility issues with my Oakley Radarlocks. It's a close fit but as long as everything is properly adjusted, you'll forget you're wearing shades or a helmet. Can't say enough good things about the Aeon!

Adjustment knob breaks off

  • Familiarity: I've put it through the wringer

Overall a good helmet. However, I've owned three of these, and the adjustment knob has broken off each one within 3-4 months of use. I never adjust the fit while riding, and I am understandably cautious when I do turn the knob. Mechanics at my local bike shop say that manufacturers discount longevity in order to make low weight claims. Come on, people. A stronger knob might add 3-6 grams. It's worth the weight.

Giro fan forever...

  • Familiarity: I've put it through the wringer

The Aeon saved my life, literally. I was t-boned during a ride... Before that, it was an extremely comfortable, super light weight, and excellent looking helmet! I would not hesitate to get another and in fact, I just did! Thanks Dan and Competitive Cyclist! Going for the orange one for visibility ;)

Legit Brain Bucket

    This is a nice lid. Was looking at Specialized helmets, but the Spec lids didn't fit my head quite right. However, the Giro lids fit comfortably, and are also stylish.

    Avg. ride time: 8h 53m per week
    • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

    Does not hold sunglasses well

    • Familiarity: I've used it several times

    I just got this helmet a couple weeks ago. Very comfortable and light. I love the adjustment mechanism. The large size does not hold my oakleys at all. It might seem like a silly thing but i'm so used to putting my glasses in my helmet for the long climbs simply with one hand and easily reaching for them when I need them. I would think that would be a design consideration with a helmet of this level. I might return it but I do feel a little guilt about this as I've been using it for a couple weeks now. Really want to really like it.

    Agreed. That was a big disappointment for me and I am still living with it. Take advantage of the awesome return policy competitive cyclist has and get yourself a helmet that holds your sunglasses.

    Avg. ride time: 11h 42m per week
    • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

    Feels Good, Looks Good Too

    • Familiarity: I've put it through the wringer

    Love the design and look of this helmet, and all the great color schemes that it comes in. This along with its super lightweight and a perfect fit make this my favorite helmet from Giro, and my favorite helmet I've ever owned.

    Feels Good, Looks Good Too

    Great helmet but costly

    • Familiarity: I've put it through the wringer

    I've been riding with my Aeon for about 18 to 24 months. Without a doubt the lightest, most comfortable helmet I've ever used. Also the the best able to keep my melon cool. This is important as I live in South Florida and regularly ride in 90 degree temps. This helmet's only downfall is it's high cost. Easily 50 to 70 dollars more than several other high end helmets. Helmets wear out (the Roc loc on mine took a dump recently) and replacing it is a substantial cost. That said, if money isn't a problem you will have a difficult time finding a more comfortable helmet than the Giro Aeon.

    One of the Best

      I purchased my first Giro "Atmos" helmet 12+ years ago. It was one of the first modern, really good looking, highly-vented, in-mold composite bike helmets made. Fast forward to today... Giro (based in Santa Cruz, CA) designs some of the best high-end helmets in the sport (atmos, aeon, air attack, synthe).

      The Giro "Aeon" helmet is a fantastic Summer helmet: extremely well-ventilated and -amazingly- light. The ultimate light-weight warm-weather helmet?

      Note: Make sure any helmet fits your head *shape* correctly. This is very important and true with any company's bike helmet. The only way to find out is to try 'em on.

      Light & Right

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

      Santa just brought me a new Aeon, and I've taken advantage of a couple of warm-ish days to ride with it. The first ride, I had to tap my head a couple of times to make sure I had a helmet on - it is that light and comfortable. I've been riding with Giro buckets for 10+ years and this is definitely their best effort. It adjusts very easily, and the straps are light and comfortable. Even with my 7 7/8ths head, I could fit a wool training beanie underneath. Fortunately, I've never had to test my Giro crashworthiness out it any serious way, but it's nice to know it's there. Take a look at one if you are thinking of a new helmet.