Giro Source vs Giro Merit: A Head to Head Comparison

In this comparison, we have a look at the Giro Source vs Giro Merit. Explaining the price difference, and where each helmet excels and which is going to be better suited to you!

A safe, light, well-ventilated helmet is what every mountain bike rider is hunting for. Here, we have two such helmets. Other than the price, what are the differences between these helmets, and which is the helmet you should go for?

The Giro Merit is the most recent helmet in the Giro line up. It sits between the Giro Manifest at the top of the half shell range, and the Source. The Source is the slightly less expensive, simpler helmet. 

Giro Source Review

For an excellent, mid-tier helmet, you can’t go wrong with the Giro Source. It is my go to for evening or shorter weekend rides. It is unbelievably comfortable, has a great fit, and you can tighten to fit in such small increments you are bound to get the helmet hugging your head.

The only downside is the weight. It can’t compare with the more pricey helmets as it doesn’t fit into that super lightweight, cloud feeling category with the likes of the Giro Merit, Specialized Ambush, Troy Lee Designs A3 etc. 

Giro Source MIPS

Designed to have all the features you need, with great ventilation and comfort, without bumping the price up with unnecessary features. Perfect for the all-mountain rider not wanting to make any sacrifices!

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  • MIPS liner
  • Exceptionally comfortable
  • Great value for money
  • Great rear coverage


  • Average ventilation

Giro Merit Review

A bit flashier than the Source, the Merit offers all you want and need from a top-tier helmet. It is light, breathable, comfortable, with excellent safety features like the MIPS Spherical. 

The downside is the cost. The Merit is a pretty pricey piece of equipment. The extra cost may only be worthwhile to you if you are likely to notice the ventilation and weight. 

Giro Merit Spherical Helmet

Highly recommended for beginners through to advanced trail and enduro riders. With MIPS Spherical, progressive layering and great coverage this is a top end helmet not to be overlooked!

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  • MIPS Spherical
  • Great ventilation
  • Lightweight
  • More ‘aerodynamic’ design


  • Limited protection of the rear of the head
  • A bit more expensive

Design and Construction

Giro has produced two rather different looking lids with the Source and Merit. The Merit looks more like a relation of a road helmet than it does the Source! 

The Merit has plenty of angular vents and a minimalist looking shell, with a relatively small amount of coverage at the rear. The Source is a little bulkier looking, with fewer vents and a deep rear coverage. Both helmets are fully wrapped with a polycarbonate shell (ie: no foam is exposed) to extend the life of the helmets.

Working our way inside the helmet, the next main difference is the foam layering. The Merit features MIPS Spherical, which has two separate layers of foam which can move independently to one another, with the Source just has one layer. 

The inner layers of the helmet are where the helmets become rather similar. Giro is well known for producing very comfortable helmets, and they haven’t failed here. Both helmets have ample of plush padding, and the RocLoc retention system means both helmets can be adjusted to fit just the way you like!


While all helmets need to meet certain safety requirements, not all helmets are created equal! Some helmets have more material protecting more of your head, some have anti-rotational impact protection systems (ie: MIPS) that can significantly reduce your chances of a brain injury, and typically you will want both of these things.  

Both the Giro Merit and Giro Source helmets have MIPS technology. The Merit goes a step further with the top of the line MIPS Spherical technology, which is a second layer within the helmet that rotates independently to the outer shell. This allows an additional layer of foam protection, provides greater resistance to rotational impacts, and has numerous other advantages over the standard MIPS liner in terms of ventilation of the helmet!

The two layers of foam, referred to as progressive layering, are made of different density materials. One layer is a harder material, which is able to mitigate energy from harder crashes, while the other layer is softer and able to reduce the energy from slower crashes. This results in a larger range of crashes in which the Merit can absorb energy and protect your head. 

The Source has a standard MIPS liner. The inner liner (which sits on your head) moves independently to the outer shell in a crash, allowing the outer shell to absorb a bit more of the energy instead of transferring it directly to your head. 

If you want to read a bit more around the MIPS and MIPS Spherical technology, see here

Giro Source

In terms of coverage of the head, the Source really excels. The back of the head is well protected by foam extending towards the neck, as well as over the temples in front of your ears. It is one of the best helmets I have come across with this amount of coverage. 

The Merit has gone a little more minimalistic, with less coverage at the back of the head (although it is still better than a road helmet) which I think could be improved. 


No doubt about it, the Merit is a lot breezier than the Source. It allows air to flow in and out easily, keeping your head pretty cool. The gap between the foam layers of the Spherical set up helps circulate the air a fair bit, and the over-brow vents push the air through. 

The Source is no weakling in this category though. The 17 vents ensure that air is still moving through the helmet. On hotter days, we would still reach for this than the Troy Lee Designs A1, or the MET Parachute MCR half shell. 


The weight difference of the two helmets is negligible. Giro claims 351 g for a size medium Source, and 360 g for a size medium Merit. Not noticeable for the average rider, and certainly not a deciding factor between the two! 

For reference though, both helmets are very light. Most top end helmets weigh in the 350g to 420 g category. 


The Source is one of my favorite helmets to have on my head. It genuinely feels like a cloud, with no pressure points and super secure. The padding is plush, and very durable. I have been wearing the Source for around two years, and the padding is still in great condition. 

The Merit is also very comfortable, with its plush ionic padding, and RocLoc Trail Air retention system. It doesn’t have the same feeling of security as it doesn’t sit as low on the head- but some may prefer this as it also helps with the ventilation!

Giro Source MIPS

Both helmets have large retention dials at the rear of the head so you can adjust the fit of the helmet as you ride, even with gloves on. And the dial works in really small increments so that you can get it to fit really well. Both have tilt adjusters so you can change how the helmet sits on your head (ie: shift the helmet towards your forehead or back of the head). 

The Source and the Merit both have anti-microbial padding, which prevent the helmet smelling, and wicks away the sweat efficiently. 



  • MIPS Liner
  • RocLoc 5 fitting system


  • MIPS Spherical
  • RocLoc Trail Air
  • Integrated goggle gripper (little bits of silicon at the rear of the helmet that hold the goggles in place). 


  • Anti-microbial padding
  • Adjustable visors (4 positions)
  • Fully wrapped shell for prolonging the life of the helmet

Final Thoughts

A helmet is there to protect your head, so this should be your number one priority when selecting a helmet. But a MTB helmet can be so much more. It can be lightweight, well ventilated, comfortable and stylish. Obviously, the greater your wishlist, the greater the price tag! So you need to determine how which benefits you prefer or which you can live without.

The Giro Source MIPS is an excellent all round helmet. It excels in safety, comfort and looks, but doesn’t have top tier airflow leading to it getting a little sweaty at times. This really is its only limitation, so if you aren’t too phased on having a warmer head (which can actually a bonus in cooler months- or you don’t do huge climbs or distances), it is a great value for money helmet, and just a great helmet in general! 

The Giro Merit Spherical MIPS ticks a few more items on that wishlist. The ventilation is superb, it’s very lightweight, as well as being safe and comfortable. It has some extra safety benefits with the MIPS Spherical technology, and this is the least expensive helmet I am aware of with this technology! It is a great helmet for trail or enduro riders who want to do longer distances, or live in warmer climates. 

Giro Merit MTB helmet review

For similar style helmets, we’d recommend looking at our reviews on the: