I love the Giro Synthe. I own both MIPS and non-MIPS versions now. I can confirm that the MIPS version fits just slightly, slightly smaller than the non-MIPS version. So if you're on the fence sizing-wise, go with the larger size.

I love the aerodynamics and quietness of this helmet. If you compare the Synthe to previous top all-around road helmets (S-Prevail, Giro Aeon, Giro Ionos), helmets I rode in for years, there is no comparison. The Synthe is significantly quieter, especially when you put your head down during hammertime.

By the way... Greg van Avermat won the Olympic Road gold and the 2017 Paris-Roubaix wearing... the Giro Synthe helmet.

I've tried several helmets this year, and I've landed on this one and am very happy. It looks pro because some of the racers in the world tour peloton use this helmet. It's lightweight and has the added bonus of being a MIPS helmet.

Initial ride was 5 hours, hot, humid, and rainy at times.
6-12% grade hour long climb it didn't get too hot.
10 minute 40mph descent it didn't get too windy.

When I first pulled this helmet out of the box, and saw almost no padding whatsoever inside and no extra padding in the box, I thought for sure that my review was going to end up being a negative one, and yet it isn't.

Giro's current top end road helmet (I'm not counting the Vanquish aero helmet), is one of the lightest and most comfortable I've ever had the opportunity to wear, because while the padding is minimal, it's perfectly situated.

A lightweight helmet is really important to me as well. I have degenerating discs in my neck, and relatively weak muscles. Because of this, any extra weight on my head can put stress on my neck muscles when trying to hold my head up in riding position. On today's inaugural ride in this helmet, I barely noticed the weight of the helmet at all.

My lack of fitness, on the other hand, I noticed right away, and while there were lots of times I was struggling on the bike, none of them were neck related. To me right now, that's worth a 5-star review.

And the added benefit of MIPS protection would bump it to a 6-star review if I had that option.

The helmet was awesome in every way but was too small so I returned it. I purchased it on sale, size small (clearance?) and it's definitely worth it if you have a small head.

Bought this helmet as a gift. Here is what they had to say about it - "One of the best helmets I have ever used. The fit is great and the ventilation is really awesome. Very comfortable even after hours in the saddle. I've been using this helmet for road rides, road races, and cx races. Love knowing I have the extra protection of MIPS."

I used this helmet for a year and a half to two years and it has been exceptional. The small size fit my 21.5" head perfect and when I recently had a bike crash it kept my head safe and it did not move from it's original position at all.

I loved my original Synthe Titanium and rode it for several seasons. Had to replace it after a crash in the fall and decided to upgrade to the MIPS for extra safety. Fits exactly the same as the original and breathes just as well. I don’t plan to ever switch from this helmet except for future renditions. Couldn’t care less about the Aero claims, but I guess it’s a plus.

I couldn't decide if I wanted to put that much money in a helmet, but I am glad I did. Researched several different helmets and finally decided on the Giro Synthe MIPS. I have been wearing a Giro Atmos II and wanted to get a helmet with MIPS. It is one of the most comfortable helmets I have worn and is very easy to adjust. The helmet looks great and I could not be more pleased.

Great colour. Helmet is nice and light. I also have a Foray and this fits the same. The Synthe is a beautiful helmet and has MIPS but I'd have to say the cheaper Foray is much the same as the Synthe and way better value. I had a crash with a Foray and wrote the helmet off but my head was good and the Foray didn't have MIPS. Personally I'm not so sure that MIPS is the great miracle life saver but maybe it is.

The Synthe is simply brilliant, and I mean that literally. You could almost miss it, which is why I love it so much. The other big hitters in the high-end helmet game (Octal, Z1, Protone, Overtake) are the figurative extroverts of the cranial protection world, and for some, this is a positive, but for the vast majority of the population, your fashion taste may be called into question. "He looks like a marshmallow." The Synthe's is always going to be the safe and classy option.

In the modern day, any helmet over $200 is going to be fantastic. They all ventilate well, they're all held to the same high safety standards, and they're all shockingly light. The Synthe differentiates itself by being delightfully straightforward. It employs the same, mind mindbogglingly simple tightening system as it's entry level siblings, instead of some contrived, bizarre systems that some of it's competitors use. (I'm looking at YOU Lazer.) One of my only gripes with this helmet is that the "sunglass garage" doesn't really work, or at least, not much better than sliding your shades into the vents.

As far as the MIPS/non-MIPS debate in concerned, yes, this helmet is slightly heavier than the non-MIPS version. Yes, it does not ventilate as well. Yes, it will occasionally catch some hair. At the end of the day though, even a marginal safety gain is worth it when you're talking about your head, and I say that as a guy who didn't even have that may brain cells to begin with. Just go for MIPS, be stingy when it comes to bottle cages, not your brain.

Really, you can't go wrong with the Synthe, and especially now, when they're on mega sale. Just go for it.

If you have any questions, feel free to reach out to me directly at jdraper@backcountry.com. (final note: the Synthe pairs wonderfully with an Oakley Jawbreaker)

I am going to buck the trend of unlimited praise for the Synthe. I mean, of course it is a nice helmet. 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 more long 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 and beautiful.

This helmet is perhaps the nicest and most comfortable I've ever had to wear. It is nearly infinitely adjustable, allowing me to custom fit the straps and cradle.

I was stoked when my brother-in-law started to get into road biking so I surprised him by buying him this helmet to help him look the part and be safe. He said it's much lighter weight and more aerodynamic than his old helmet and it doesn't even feel like he's wearing anything. I was even happier I bought it for him b/c it literally saved his life when he crashed his bike earlier this week. It's a great helmet and I bought him another one to make sure he continues to be safe!

Helmet is indeed very light. You do forget you have it on.
I have been wearing Giro helmets since 1992 and the tech has come a very very long way since those days.
So far the warmest day I rode in was in the mid 80's and ventilation was good enough. I never felt it being warm. It was on rolling to flat terrain. I have not done any climbs in the heat, yet.
The fit. It has changed slightly. I have been wearing Giro large size helmets for as long as I have owned them; however, this helmet is just a tad narrower than other Giro helmets I've owned. Enough to notice but not at all uncomfortable. I compared it back to back to my Atmos to ensure I was not crazy. And yes, it is indeed narrower.

Accurate fit per sizing chart (medium), looks good, colors are tasty, nice strap and clasp

It looks good and it feels good. It seems to help prevent sweating on the brows/forehead and wick any sweat off the side. I usually have issues with helmets accumulating sweat that drips into my sunglasses – but so far, I haven't had that issue with the Synthe. I forget it's even on my head.

Great fit right out of the box, with very little adjustment needed. Unlike all of my other helmets, the buckle stays put, so the chin strap doesn't loosen and constantly need adjustment. Light weight, fits great. Thanks for the sale price, too!

The Giro Synthe Mips is a slick helmet! As others have noted, the size adjustment fits a wide range of head shapes, it's plenty light, and also well ventilated.

I haven't tested out the crash worthiness yes (knock on wood!), but I've left behind a long wake of broken Giro helmets that demonstrate the quality of build and protection.

Everything is pretty good, it looks great, it fits good, well ventilated