Today, 6D officially announces its entry into the lightweight full-face MTB helmet arena with the carbon Alterra. At 710 grams and $395, it's been a long time coming for the brand that has elevated helmet safety in both cycling and motocross. Dig into the specs and info below followed by our first-ride impressions.
Highlights
- Patented Omni-Directional Suspension™ (ODS)
- In-Molded carbon fiber chin bar and internal roll cage
- Polycarbonate shell
- Multi-Impact EPP inner Llner and EPS outer liner
- EPP sternum and clavicle crash pads
- lonic+ Antibacterial Comfort Liner
- Goggle compatible with under-visor storage
- Directional venting and sub-channeling
- Extra-Large rear directional exhaust vents
- Fidlock closure system
- 3-position snap-away adjustable visor
- Travel bag included
- Multiple comfort liners and pad sets
- Sizes: XS-S (53–56cm), M-L (56–59cm), and XL-XXL (59–62cm)
- Six colorways
- Weight: 710g M/L
- MSRP:$399 USD
April 8, 2025 (La Habra, Calif.)—6D Helmets, pioneers in helmet safety technology and design, proudly introduce the all-new Alterra lightweight full-face enduro helmet. Four years in the making and building on their deep roots in motocross and recent success at the Olympics in BMX and the World Cup Downhill series, 6D’s latest innovation delivers unparalleled protection, comfort, and performance for enduro riders.
At the heart of the Alterra helmet is 6D’s patented in-helmet suspension and energy management system called Omni-Directional Suspension™ (ODS). ODS reduces energy transfer to the brain over a wider range of energy demands, including low-, mid-and high-velocity impacts for both linear and angular acceleration. This is achieved through the use of a suspended dual-liner assembly that can displace and shear in any direction upon impact. The system has been rigorously tested and proven to offer superior impact mitigation across multiple disciplines.
The Alterra’s in-molded carbon fiber chin bar and carbon internal roll cage further enhance structural integrity while keeping the design lightweight, making it the go-to choice for riders seeking both strength and comfort on the trails.
"With all of the exceptional benefits of ODS and its suspended liner system, 6D remains at the forefront of rider safety and performance. We’re excited to be adding another cycling helmet to our collection," said Bob Weber, CEO and co-founder of 6D Helmets. "The Alterra helmet upholds 6D’s trusted safety standards while also delivering the lightweight construction and superior ventilation that riders demand."
The Alterra helmet is designed with directional venting and sub-channeling that optimizes airflow throughout the helmet, helping riders stay cool during intense rides. The extra-large rear directional exhaust vents efficiently dissipate heat, while large over-brow ventilation channels provide a steady flow of air, enhancing comfort during long rides.
Additional features include a polycarbonate shell combined with a multi-impact EPP inner liner and an EPS outer liner for maximum protection. The helmet’s lonic+ antibacterial comfort liner is designed to maximize airflow and maintain hygiene, while its goggle-compatible under-visor storage and glasses compatibility add to the helmet’s versatility. The Alterra helmet also incorporates a Fidlock closure system for secure fastening and a 3-position snap-away adjustable visor for customization.
Each helmet comes with three cheek pad sizes and two liner and neck roll sizes, allowing riders to dial in their ideal fit. The Alterra is available in three sizes—XS-S (53–56cm), M-L (56–59cm), and XL-XXL (59–62cm)—and comes in six distinct color options to suit every rider’s style.
The 6D Alterra helmet exceeds CPSC/EN1078/AU/NZS 2063 safety standards and meets the NTA 8776 E-Bike standard as well as the ASTM F1952 (DH) and ASTM 2023 (BMX) standards. Backed by a 3-year limited warranty, the Alterra helmet is available now and is set to redefine safety and performance in the enduro market.
First Ride Impressions
I've had the chance to spend a handful of rides in cool weather in the 6D Alterra, and my first impression is that it is incredibly light and very comfortable. Since interviewing Bob Weber, 6D's founder, a couple years ago and learning about their development story, I've continued riding in 6D's ATB-2T half-shell during trail rides. The safety of the 2T made it an easy decision to wear, despite being heavier and larger looking than other half-shell trail helmets. The 2T fit my head well and the weight was never an issue. When the Alterra was announced, I was excited to try it out, as most trail rides these days warrant full-face coverage.
I chose to wear the 2T because of 6D's ODS design that protects your noggin against fast and slow impacts. It's more than just a rotational, two-dimensional slip-plane. There is also *suspension travel* built in to help mitigate impacts on the head and brain that foam alone can't. Not every mountain bike crash is so high-speed that it will crush the foam the way it's designed. Additionally, most modern tests only measure a helmet's effectiveness at these higher impact speeds. Slower speed hits can still result in concussion or head injury, and 6D's tests prove ODS will perform better than other designs under the same conditions.
I wear a M/L in the 2T helmet, and it hugs my head well, so I requested the M/L Alterra for testing. Unfortunately, my head wouldn't quite fit into the pocket of the M/L Alterra shell even with the smallest pads installed. A L/XL was sent out and it ended up fitting great with the 18mm pads. The helmet comes with two pad thicknesses, so most riders should be able to dial-in fit even if you're between shell sizes.
Once the helmet was on, it was easily forgettable thanks to its light weight and pad configuration. The padding relief around the ears gives the Alterra a feeling similar to that of a half-shell. The pads don't put any pressure on your ears, and there are no pads to squeeze your ears past when putting the helmet on.
The Alterra's svelte nature gives the illusion that you're not wearing a full-face helmet. At 710g for a size medium, it might not be the lightest full-face enduro helmet, but its very competitive. For comparison, Fox's Proframe RS weighs 820g, TLD's Stage weighs 690g, and Smith's Mainline weighs 770g (for size M helmets).
A Fidlock closure is always a welcome feature, and the padded strap covering the strap is a nice touch to relieve any under-chin pressure points.
I only rode the helmet in temperatures of 45-60F, so I can't speak to how well it stays cool on hot days yet. The vents are ample and on chillier rides, I wished for more coverage as wind would breeze through. My prediction is that the Alterra will not be overly warm, but time will tell. Goggles fit nicely and the 3-position visor makes it easy to store the goggles underneath.
During the testing period, I learned that Darren Murphy, founder of PUSH, was in a pre-production sample of the Alterra and had a serious crash into rocks while wearing it. Darren says, "I was solo in the backcountry and had the biggest crash I can remember. Huge hit to the head as I went head-first into rocks. Not going to lie, I shed a couple tears after I pulled the lid off. Was stunned by the helmet's performance. Felt really lucky." Below is a photo of the helmet after Darren's crash.
Testing helmets for Vital rarely (and thankfully) leads to actual crashes to test their effectiveness. And while every crash is different, Darren's story, while anecdotal, is relevant to our first ride feature, and I wanted to share it.
Maybe the only hangup for some with the Alterra could be its $395 price tag. For comparison, the Fox Proframe RS retails for $359.95, TLD's Stage for $319.99, Endura's MT500 for $299, and Smith's Mainline for $310. The Alterra is one of the more expensive options, but not by a landslide. Personally, I believe in the safety of 6D helmets, and am happy to pay more for that safety. It's your brain after all, it's worth the extra money.
What's The Bottom Line?
The Alterra takes 6D's trusted and effective ODS system and packages it into a breathable, lightweight enduro full-face helmet. It has all the bells and whistles you'd want from a premium helmet, matched with a comfy fit that can make you forget you're wearing a full-face. And most importantly, it delivers safety that's class-leading against various impact speeds. We were big fans of 6D's ATB-2T trail helmet, but moving forward, the Alterra will be our go-to for most rides, as you don't have to sacrifice comfort to receive extra protection.
In 2023, we talked with 6D founder, Bob Weber, and learned a lot about helmet development and helmet standards.
View key specs, compare enduro helmets, and review the 6D Alterra in the Vital MTB Product section.
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4/8/2025 9:00am
View replies to: 6D Helmets Enters the Lightweight Full-Face Game with Alterra - FIRST RIDE
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