Apparel Gear Riding

5 Reasons to Switch (One K Defender Air Helmet Review)

one k defender air helmet
Written by Horse Rookie

A Well-Adjusted Approach to Safety and Fit

After more than 30 years in the saddle, I’ve owned more than my fair share of helmets. I was lucky enough to begin childhood lessons at a helmet-savvy English barn alongside my father, who also rode and adopted an unwavering commitment to safety. 

Wearing a helmet has been a requirement, not an option, as long as I’ve been riding horses.

Though we always “protected our melons,” my father and I tended to purchase budget brand helmets like Troxel. They got the job done, and they’re far superior to bike helmets (or no helmets!).

I’ve never owned a “high end” horse riding helmet, despite keeping an eye on all the advancing safety technology. Now, between working cows and jumping, it felt like now might be the time to invest in an upgrade. After hearing me hem and haw over which brand and model to get, my lesson partner decided to gift me a gorgeous One K Defender Air for Christmas!

Quick Look: One K Defender Air
  • 9/10
    Safety - 9/10
  • 8.5/10
    Design - 8.5/10
  • 9/10
    Ventilation - 9/10
  • 7.5/10
    Comfort - 7.5/10
  • 9/10
    Fit - 9/10


There’s no better place for your money than a high-quality riding helmet. The Defender Air delivers both cutting-edge safety technology and a custom-fit air pump system.

What We Love: 

  • ASTM/SEI F1163-15 safety certified
  • Air pump helps you achieve the perfect fit
  • Washable quick-dry liner
  • Chip strap “tail” velcros in place
  • Beautiful design that suits any discipline

What We Don’t:

  • Chin harness angled a bit too far forward
  • Not compatible with One K magnetic sunglasses
  • Doesn’t have MIPS technology
one k defender air helmet

Click to see the Defender Air at Amazon

Meet the One K Defender Air

One K is a highly-respected equestrian brand that combines the latest safety technology with modern design. There are 5 different models within their Defender product line, as well as a Racer Skull Cap and CCS with MIPS helmet.

As I turned this helmet over in my hands, I could immediately tell that it was the nicest one I’d ever owned.

The Defender Air model is marketed as the “Perfect Equestrian Riding Helmet Fit for Inbetweeners,” a phrase that makes me chuckle because it’s so true! Many riders struggle to choose from preset helmet sizes that are slightly too big, or slightly too small, as seasons change.

one k defender air helmet monster

Monster approves!

5 Reasons to Switch

Safety Comes First

Rhinestones may catch the judge’s eye in your dressage test, but they won’t protect your noggin during a fall.

That’s why your primary consideration when helmet shopping must be safety — not style. 

one k defender air helmet

Unboxing my new One K helmet

The One K helmets are subject to three different safety tests (see below), and their products score above the required standards on all three. That’s why One K is approved by the CE norms VG01 and is ASTM/SEI F1163-15 certified.

one k helmet testing

Click to learn more about One K safety testing (Source: One K)

Innovative Air Pump System

Given the name of this helmet, it’s no surprise that its defining feature is its air pump system. By manually inflating or deflating the liner, you can achieve more comfort and a custom fit.

Round or oval head? Medium-largish or smallish-medium? Hair down or show bun?

Simply press the small button to let air out of the lining, or squeeze the air pump until you’ve added enough air to snug up the fit.

one k defender helmet air

Press to deflate

The Defender Air features three hidden air chambers in the liner, which means adjustments are evenly distributed around your head. Plus, the liner is washable quick-dry, moisture wicking, and anti-microbial.

one k defender air pod

Squeeze to inflate

Ready to give it a try? Click to see the One K Defender Air at Amazon.

Maximum Ventilation

With two side, two front, one back, and two center stripe vents, this helmet definitely helps cooler heads prevail.

Whether you’re out on the trail or competing in the blazing heat of summer, ventilation is essential to keeping you cool, comfortable, and thinking clearly.

one k defender air vents

Stainless steel mesh won’t rust

one k defender air

The vents enhance the design rather than distract from it

Check out the 10 best horse riding helmets for dressage, jumping, etc.

Comfort Comes Standard

The air pump system is only one of the design components designed to make this helmet super comfy. For example:

  • Two Head Shapes: Choose either Regular/Round or Long Oval, depending which fits your head shape best.
  • Ten Size Combos: Select XS, S, M, L, or XL, each of which is available in the round or oval variety.
  • Comfort Harness: It’s padded with synthetic suede lining, hook and loop adjustment, and a fast-tex buckle.
  • Cushioned Liner: Super soft and breathable, the liner isn’t itchy against your skin.
  • Sun Visor: Skip all that squinting thanks to the generous, yet low-profile, visor.
one k defender air helmet

Cushioned harness and liner

one k defender strap

Velcro holds your chin strap in place

Accident Replacement Policy

Helmets are made to absorb the energy of an impact, and any unit that suffers an impact should be destroyed (read: NOT resold) and replaced immediately.

Even helmets that haven’t been involved in any accidents should be replaced every five years.

Here’s the good news: One K has an Accident Replacement Policy that allows riders to replace compromised helmets, without paying full price, up to three years after purchase.

one k defender air

Replace any helmet involved in a fall immediately

No Helmet is Perfect

Every helmet — and every head — is different, and personal preferences largely dictates the “best” brand and model for you. For me, here are a few things I find less than ideal, but none of them outweigh the benefits.

  • Chin Strap Angle: I’d love if the harness was about 1/2 inch further forward on the helmet so that the chin strap was more directly below the harness versus angled forward. 
  • Price Point: This helmet will set you back several hundred dollars, as opposed to budget brands like Troxel that are typically less than $100.
  • Not Klick N Go Compatible: Some One K helmets work with their magnetic sunglasses, but the Air model isn’t one of them.
one k defender helmet

The harness could be moved a bit further forward

Caring for Your One K Helmet

Here is some handy guidance when it comes to extending the life of your new helmet. 

Exterior care:

  • Brush or wipe off any loose dirt or debris.
  • Use water, mild soap, and a lint-free cloth to clean the exterior.
  • Allow your helmet to air-dry out of direct sunlight.
  • Use a compressed air can to blow out dirt and dust from the vents.

Interior care: 

  • Allow your helmet to air-dry prior to placing it in a storage back or tack trunk.
  • Use a helmet deodorizing spray on the liner to kill odor-causing bacteria.
  • To remove sunscreen, makeup, or grease build-up, other mainstream cleaners may work better. 
  • Liners can be removed and cleaned in the washing machine. Just be sure to air-dry it in a cool, shaded place.
  • Wipe the chinstrap clean with a moist, lint-free cloth.
  • Whether after cleaning or riding, be sure the helmet liner is fully dry before wearing again.


  • Use a helmet cover or bag to minimize scratches and dust build-up.
  • A helmet rack is another good option, as it helps the helmet air-dry when not in use.
  • Avoid excessive heat (e.g. in your car during summer) and direct sunlight.

How long do One K helmets last?

Some of this depends on usage and whether or not you take a serious fall. If your helmet ever impacts the ground (or something equally hard), you need to replace it because the integrity of the helmet becomes compromised after impact.

Even if you don’t take a fall, you should replace your helmet every five years. This period of time can be shorter if you don’t take good care of it or if the helmet has a lot of sun exposure. Helmets, like anything you wear, degrade over time thanks to sweat, oils, and dirt.

Do all One K helmets have MIPS?

Not all One K helmets have MIPS, but they do have a lot of options that include MIPS. They have one line in particular, the One K CCS with MIPS technology. This line includes a standard helmet, a wide-brim helmet, and a youth helmet.

The CCS line also offers a lot of fun color and style options if you want to play around with the look of your top panel.

If you like their Avance line, they offer a wide-brim helmet with MIPS. Even without MIPS, One K helmets are known for their safety.

Parting Thoughts

The more you love horse riding, the more you want to be able to continue doing it. That means taking safety seriously and wearing a certified helmet every time you swing into the saddle. Budget-conscious brands are good options when you’re starting out, but it’s worth upgrading to a nicer helmet with the latest technology when you’re able. 

one k defender air helmet ride

Enough talk… let’s ride!

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About the author

Horse Rookie

I began riding horses at age six, and I'm just as infatuated (OK, more!) with the sport decades later. My AQHA gelding exemplifies the versatility of the breed -- reined cow horse, reining, roping, ranch riding, trail, dressage, and jumping. We're also dipping our toes (hooves) into Working Equitation!