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Klim F4 ECE Stealth Helmet
  • Klim F4 ECE Stealth Helmet - Stealth Black
  • Klim F4 ECE Stealth Helmet - Stealth Black
  • Klim F4 ECE Stealth Helmet - Stealth White
  • Klim F4 ECE Stealth Helmet - Stealth White

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Video Reviews (3)

Klim F4 ECE Stealth Helmet Videos

Klim F4 ECE Stealth Helmet

In an effort to make one of the most comfortable motorsport helmets on the market even better, Klim has been collecting racer, customer and dealer feedback for improvements on the F4 helmet since it’s introduction.

This is the ECE Rated helmet - It is not DOT Approved.

Snell M2010 Rated helmet also available. ECE Version is nearly 1 pound lighter than Snell F4.

This newest version has implemented these improvements and the result is a helmet that is even more comfortable and better-fitting than the original F4. Intake and exhaust ports have been significantly enlarged allowing more air to enter and exit the helmet. The EPS liner shape has been modified in three ways. The cranial shape at the top of the helmet has been altered to allow a better fit on a wider variety of head shapes and also helps keep the helmet positioned correctly. The three large air channels that run laterally through the helmet were already some of the deepest offered in any helmet, but we have made them deeper in this version, allowing even more air to pass over the head and out of the helmet. The plenum chamber (inside the EPS) has also had its channels deepened, allowing an overall greater bandwidth of air to pass through the EPS to the rider’s head. 

The comfort liner has been completely redesigned to implement the latest technologies in moisture-wicking fabrics. Moisture-wicking foam has strategically-placed perforations allowing a much greater amount of air to pass through the liner while enhancing comfort. With an unprecedented 41 air-craving intakes, the F4 again establishes the newest standard in helmet ventilation technology. The helmet design is optimized to effectively channel air into the helmet where it is assisted by a network of air-channels in the the EPS liner to maximize airflow over the entire head. The result is a dramatically cooler and drier riding experience. The pocketable WINDSTOPPER liner can be snapped onto the comfort liner in colder weather, which will still allow moisture to be moved away from the head while preventing air from directly contacting the head.

Safety standards have been exceeded not only through the use of aerospace materials, but also in the design. The F4 exceeds ECE 22.05 standards, but not US DOT.

Third Generation F4 Upgrades Include:

  • Improved fit
  • Improved ventilation via deeper air channels in the EPS
  • Improved ventilation via larger intake and exit ports
  • Improved fit of comfort liner
  • Improved comfort liner ventilation via airflow perforations
  • Improved moisture-wicking comfort liner via enhanced moisture-wicking fabrics and perforated foam
  • Bold new graphics and colors


  • Ram air induction technology with 41 air-craving intakes, the F4 sets the newest standard in helmet ventilation technology
  • Non-intrusive eye port increases field of vision
  • Ram air-induction scoops not only mine air as it flows over the helmet, but helps to increase the structural integrity of the helmet
  • Pressure chamber network in eps helps to maximize airflow over the head
  • Zonal fiber select construction with aerospace fiberglass, carbon fiber and Kevlar ensure a safer helmet
  • Removable cheek pads
  • Removable comfort liner
  • Exceeds ECE22.05 standards
  • Moisture-wicking foam liner and liner material

Included with Helmet:

  • Cold weather liner with Gore Windstopper technology
  • Included Windstopper liner is small and pocketable, snaps onto foam comfort liner
  • Breath deflector
  • Deluxe nylon carrying bag
  • Fleece-lined comfort collar and beard flap
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Klim F4 ECE Stealth Helmet 4.5 5 2 2
If you ride on the surface of the sun, this helmet will help cool you down I live and ride the desert around Phoenix, AZ. Even with early AM rides, we regularly see 100 degree plus temps towards the end of the ride. Compounding the problem, the single track I enjoy is typically slow and technical. My current helmet, an Arai VX Pro3 is excellent, but lacks the airflow necessary for these conditions. Enter the Klim helmet. On the slow technical stuff, the top vents act as a chimney, helping bleed off heat. When the pace pics up, those same vents help clear the sweat and is as close to an AC unit you can get out there. The fit...My Arai is an XL with smaller cheek pads. The KLIM is an XL as well and both are perfect. Both helmets are light, but the KLIM has a more balanced feel and weighs less. I prefer the chinstrap of the KLIM. Liners are comperable, but the Arai is probably a little better since you can easily customize the fit with premade cheek pads and such. The value... This is a nice helmet on it's own. But Klim sweetened the pot with the extras. This kit includes the nicest helmet bag I've ever seen come with a helmet. Not a microfiber bag, but a full on felt lined/padded cordura bag with compartments for your googles, goretex windstopper (included), cold weather breather box (included), extra visor (included), and room for more. The bag has big grommets in it so your stinky lid can breath and dry out when you put it away. Tradeoffs? The goggle opening on this helmet is huge, which is good for airflow, but leaves you a little more exposed. Basically, the area between the bottom of your goggles and above your jaw is a bit exposed. Bigger goggles solves this problem somewhat. Wind noise is tremendous if you are tempted to slab it to the trail...I wouldn't recommend using this helmet for the highway for that reason. Technically, it's not a DOT helmet...so if you did use it on the road and something unfortunate happened, I wouldn't want to tangle with the insurance over it. Here in AZ DOT helmets are required by law, but I am not worried about johny law citing me out on the trail. It's more of a liability concern on the road than anything else. Bottom line, if you need a trail helmet with killer airflow, light weight, and comfort features...this is a great choice. I also considered the Airoh aviator, but the prices tipped the scale in favor of the Klim. August 18, 2014
You will get dirty & wet I have used this on two separate week-long adventure trips. The first one in SoCal was shockingly cold. Others longed for my google set up compared to their street helmet/visor configuration. (I bought Scott goggles with an integrated fan and tear-off lens covers). The helmet worked well for this applicaiton. Next time, I will put in the skull cap windstopper to keep warmer. The second week was in Ecuador. The driving and the weather was as about as varied as could be. 1) Freeway: I eventually had to take the visor off. At highway speeds, it forced the helmet onto my head that became unbearable after two days. Turning my head at all (like to check on my buddies in the group) would catch the wind in another uncomfortable way. 2) Offroad: If I didn't have the windstopper in around the nose installed, I would end the day with a dirt mustache. 3) Weather. In any case, I felt rain around googles that hurt at freeway speeds. See those big vents on the top? They are rain gutter collection points that I had to tape up for this trip. I was complimented on the design both in the US and in Ecuador. People think this looks cool. It is a lot lighter than my c3. March 22, 2014
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Have a functionality, fit, or otherwise product-specific question about the Klim F4 ECE Stealth Helmet? Ask it here! If you have a customer service or shipping question, please direct it to our Customer Service department.

Klim F4 ECE Stealth Helmet
Already Asked: 3 Questions, 5 Answers
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RevZilla Store asked: Why did you choose this?
owen r: ventilation and weight! Feb 16, 2015
Stephen T: I like Klim gear Jan 8, 2015
Jeff P: Supposed to be the best airflow available in a MX helmet. Riding in 100 degree + weather, I need all the ventilation possible. I also considered the Airoh aviator due to it's light weight and ventilation, but ultimately went with this based on price and advice from friends. Jul 29, 2014
A shopper asked: what does this helmet actually weigh? Aug 30, 2013
Answer this · Send to friends Good question? Yes (1) No (0)
Brian L: 3.03 lbs according to my kitchen scale Sep 11, 2013
Reply to Brian Good answer? Yes (1) No (0)
A shopper asked: Had anyone else had a problem installing the breath deflector in this helmet? The snaps on mine barely even hold the cheek pads in and when I put the deflector in the snaps will not snap!!! I just can't believe klim would let something like this out the door!! Any info would be awesome!! Thanks in advance!! Jan 2, 2015
Answer this · Send to friends Good question? Yes (0) No (0)
Richard K: I have three of the F4 helmets and do not have any problems whatsoever. You mus have defective snaps..... Jan 5, 2015
Reply to Richard Good answer? Yes (0) No (0)


We highly recommend finding a cloth tape measure and taking the time to take these measurements.  Klim sizes will not necessarily correlate with fitment in other brands.

Klim Helmet Sizing

Hat Size 6 5/8" - 6 3/4" 6 15/16" - 7 3/16" 7 1/4" - 7 3/8" 7 1/2" - 7 5/8" 7 3/4" 7 7/8" 8 3/8"
Head Circumference (In) 20 1/2" - 20 7/8" 21 1/4" - 21 11/16" 22 1/16" - 22 7/16" 22 13/16" - 23 1/4" 23 5/8" - 24" 24 7/16" - 24 13/16" 25 3/16" - 25 5/8"
Head Circumference (Cm) 52 - 53 54 - 55 56 - 57 58 - 59 60 - 61 62- 63 64 - 65

Sizing information is provided by the manufacturer and does not guarantee a perfect fit.

Click here to see the full Klim Size Chart
Product Style RevZilla Item # Manufacturer Product # Availability
Stealth Black / MD 911982 5106-001-130-002 In Stock: Usually ships in 1-2 business days
Stealth White / MD 911627 5106-001-130-003 In Stock: Ships within 24 hours
Stealth Black / LG 911629 5106-001-140-002 In Stock: Ships within 24 hours
Stealth White / LG 911986 5106-001-140-003 In Stock: Ships within 24 hours
Stealth Black / XL 911631 5106-001-150-002 In Stock: Usually ships in 1-2 business days
Stealth White / XL 911632 5106-001-150-003 In Stock: Ships within 24 hours
Stealth Black / 2XL 911633 5106-001-160-002 In Stock: Usually ships in 1-2 business days
Stealth White / 2XL 911634 5106-001-160-003 In Stock: Ships within 24 hours
Stealth Black / 3XL 911638 5106-001-170-002 Out of Stock
Stealth White / 3XL 911639 5106-001-170-003 In Stock: Usually ships in 1-2 business days