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Item # GIR0329

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Item # GIR0329


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, you know why this is a concern. It seems impossible that a near-weightless thing like the Prolight offers adequate protection. Amazingly, though, it passes the CPSC testing just fine.

The Prolight tips the scale at 200 g, 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 g (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 thermoformed SL Roll Cage reinforces the Aeon for maximum safety, yet it's 49% lighter than the Ionos' composite sub frame.

The Giro Aeon 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 Small, Medium, and Large and comes in five color combinations -- Black/Charcoal, Blue/Black, Highlight Yellow/Black, Matte Titanium/Silver, Red/Black, and White/Silver.

  • Thermo-formed SL Roll Cage reinforcement provides structural integrity without adding excess weight or hindering airflow
  • Roc Loc 5 fit system is easy to adjust and anatomically cradles the head for long-term comfort
  • 24 Wind Tunnel vents and internal channeling direct cooling air through the helmet
  • X-static padding wicks moisture from the head, and is washable to prevent foul odors

Tech Specs

Adjustable Vents:
Fit Adjustment:
Roc Loc 5
Claimed Weight:
222 g
Recommended Use:
Manufacturer Warranty:
1 year

Size chart


Adult Cycling Helmets
 SMLXLAdult UniversalWomen's Universal
Head Circumference 20 - 21.75in
(51 - 55cm)
21.75 - 23.25in
(55 - 59cm)
23.25 - 24.75in
(59 - 63cm)
24 - 25.55in
(61 - 65cm)
21.25 - 24in
(54 - 61cm)
19.75 - 22.5in
(50 - 57cm)
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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Giro Aeon Helmet

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Here's what others have to say...

5 5

The Best

  • Familiarity: I've put it through the wringer

This helmet is just top. It's super f***ing light and feels like the greatest thing ever sitting on your head. The adjustably is perfect. I mean, there is not a single thing wrong with this helmet

4 5

light great airflow

took me a while to get this helmet adjusted right but grew into it - nice product very light very green

4 5

Awesome Helmet

Each head is different but for me the Giro Medium helmets fit me well. Head measure 22.75 inches around. I am closer to going to a large and large fit well with a hat or cover. This helmet is well designed and very lightweight. I gave it 4 stars as it is very expensive. Two things I do not skimp on when buying cycling gear, helmets and tires.

5 5

I freaking LOVE this helmet!

I've had this helmet for about 6 months now and I can't say enough good things about it. It fits perfectly, is very comfortable, and works perfectly for riding in warm humid climates like where I live. Air flow through the helmet is great. My wife has a Specialized S-Works helmet, which everyone says is one of the best out there, and I actually think mine is better.

5 5

Giro Aeon Helmet

Just replaced my destroyed Ionos with the new Aeon. The new helmet is better in every way. Its incredibly light. The new straps are easily adjusted and the Roc-loc is secure and easy to operate. The vents are huge! Thank-you for the speedy free delivery1

5 5

Thumbs Up!

Just received my 2012 Aeon a couple of weeks ago. The air flow is awesome ( killer compared to my old Louis Garneau). And so light it's unbelievable. The Roc Loc micro adjust works great and conforms to my head nicely. I weighed my medium ( my head is 58 1/2 cm) at 227g. I'm sure if i cut the straps to length I'd save a couple of more grams.

Over all a great helmet with aggressive design.

5 5

Giro Aeon Helmet saves the day

I bought this helmet as a present for my Brothers birthday. He recently put the helmet to a full test by taking a really nasty spill and smashing his head into the ground. The helmet was destroyed but his head had not a scratch. Needless to say I'm a Giro fan for life.

Responded on

once adjusted correctly this helmet is light and good airflow

My head circumference is 23.5 inches. Would...

Posted on

My head circumference is 23.5 inches. Would I be OK with a medium or should I try a large?

Responded on

I ended up getting a Large and it fits perfectly. Just used the chart on the Giro website. Best helmet I've ever owned. Comfort and venting is outstanding. No regrets with this purchase.

5 5

Takes a licking, but keeps on ticking

A recent cycling mishap resulted in two fractured ribs and pneumothorax and three days in the hospital. While I busted my Aeon in three places, I did not end up with a head injury. I will not even blink when I dole out $250 dollars for my next Aeon.

4 5

Giro Aeon Helmet is the goods, but the Roc Loc 5 is not...

Giro Aeon Helmet is a good to go helmet, light and breathable. No stuffy IGLOO on your head with this DADDY. My only issue is with the the Roc Loc 5, which secures the helmet at the back of the top of your neck. I am on my 3rd one now and I have barley had this helmet for 9 months. That is under warranty form GIRO, but it is a pain replacing them. Never had a problem with the Roc Loc 4. If GIRO fine tuned the Roc Loc 5, this would be the only helmet on my head. A good friend of mine has the exact same problem with his Roc Loc 5, so that chisels away at the user error issue. I hope that GIRO improves the Roc Loc 5 for 2012, or maybe I will be back to wearing IGLOO's again. Then again, all my beer will get warm... no we can't have that.

5 5


I think it may be the best helmet on the market,light as hell and fits like a glove.I bought size MED my head size is 7and1/8.

5 5

Great Helmet

The helmet is great! It is super light; I barely notice it is on my head. The venting is superb, we have been getting clobbered with 100 plus degree days in the NJ and this helmet has kept me cool during my rides. I’m convinced the venting keeps me cooler than if I were wearing no helmet at all, which I will not do, even for testing purposes. However, the way the vents are cut makes it feel like you have ceiling fan above your head. I am basically trying to say that the helmet is very lightweight and the venting is great. The new material used for the straps makes a huge difference in comfort. They are super lightweight and feel really good against my face and chin, I hardly notice they’re there as well. The RocLoc 5 system is a vast improvement over the older systems. It lets you micro dial-in the tension adjustments. Overall I could not be more pleased with this purchase. It was expensive but worth every penny in my opinion because head protection is the most important thing when riding. Shorts, gloves, shoes, etc. are all secondary to head protection IMHO.