Mips Helmets · Defender · Avance Wide Brim · Custom Color
One K Riding Helmets
Mips CCS helmets you can color your way, the classic Defender, the sun-shading Avance Wide Brim and junior helmets for young riders, in regular and long oval fits. Premium Brands for Less, with new deals every day.
Updated October 2026
One K Helmets by Line
Customize Your CCS Helmet
Find Your Fit
One K Size Chart
| Size | Head (in) | Head (cm) | Hat size |
|---|---|---|---|
| X-Small | 20.1–20.5 | 51–52 | 6⅜–6½ |
| Small | 20.9–21.3 | 53–54 | 6⅝–6¾ |
| Medium | 21.7–22.0 | 55–56 | 6⅞–7 |
| Large | 22.4–22.8 | 57–58 | 7⅛–7¼ |
| X-Large | 23.2–23.6 | 59–60 | 7⅜–7½ |
| XX-Large | 24.0–24.4 | 61–62 | 7⅝–7¾ |
| Size | Head (in) | Head (cm) | Hat size |
|---|---|---|---|
| X-Small Jr | 18.5–18.9 | 47–48 | 5⅞–6 |
| Small Jr | 19.3–19.7 | 49–50 | 6⅛–6¼ |
| Medium Jr | 20.1–20.5 | 51–52 | 6⅜–6½ |
Not sure of your size? Our Helmet Buyer's Guide shows how to measure. Every One K size comes in regular oval and long oval. Between sizes? X-Small, Small and Medium share one shell, as do X-Large and XX-Large, so a refit liner can take your helmet up or down a size.
In the Spotlight
The One K helmets our riders reach for most
Best-Selling One K
Mips CCS, Defender and Avance helmets, led by the Mips CCS
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One K MIPS CCS Helmet - Black Matte
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One K Defender Helmet - Black Matte
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One K Kids' Defender Jr Helmet - Black Matte
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One K Avance MIPS CCS - Black Gloss
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One K MIPS CCS Avance Wide Brim Helmet - Black Matte
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One K Defender Chrome Stripe Helmet - Black Matte Chrome Stripe
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One K Avance Wide Brim Helmet - Black Matte
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One K Defender Rose Gold Stripe Helmet - Black Matte Rose Gold Stripe
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One K Defender Suede Helmet - Black Matte
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One K MIPS Jr CCS Helmet - Black Matte
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One K Defender MIPS CCS - Black Gloss/Black Crystals
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One K Avance Wide Brim Rose Gold Stripe Helmet - Black Matte Rose Gold Stripe
The One K Edit
Four ways to wear One K
Mips CCS Helmets
Mips Protection in a Helmet You Can Color Your Way
The Mips CCS Helmet is the One K our riders buy most: a matte polycarbonate and ABS composite shell with Mips, a washable, quick-dry liner, stainless steel mesh vents and a padded harness with a Fastex buckle. The Avance Mips CCS and the Defender Mips CCS bring Mips to those two shapes, and the Mips Jr CCS sizes it for younger riders.
CCS stands for Custom Color System. Swap the front shield, the vent stripe rail and the top panel to change your helmet's look, from schooling black to stable colors for the show ring.
The Defender
The Classic One K, From Schooling to the Show Ring
The Defender has a polycarbonate and ABS composite shell, a washable, moisture-wicking, anti-microbial liner, stainless steel mesh over seven vents and a padded harness with synthetic suede lining. It comes in matte black and brown, with chrome or rose gold stripes, and in synthetic suede.
For smaller riders, the Kids' Defender Jr has a smaller internal diameter, a thicker padded liner and a chin strap 15 mm shorter than the adult sizes.
Avance Wide Brim
A Wider Brim for Sunny Days in the Saddle
The Avance Wide Brim takes all the features of the One K Defender and adds a wide brim for more coverage from the sun. It comes in matte black and with chrome or rose gold stripes, and the Mips CCS Avance Wide Brim adds Mips and Custom Color System parts, in black, navy and grey.
For bright days, the Klick n Go Sunshield attaches magnetically to compatible One K helmets, fits over most prescription glasses and comes in a zippered case.
Custom Color System
Over 2,100 Looks From One Helmet
Top panels come in matte, gloss and metallic colors, plus Designer panels with vintage prints. Front shields come in solid colors and a crystal version, and the vent stripe rail and crystal accessory rail finish the look. One K says the mix-and-match parts can create over 2,100 different looks.
Refit liners change the fit of a One K shell: use a Medium shell with a Small or X-Small liner, for example. They are handy for growing children, shared helmets, or riders who wear their hair differently for schooling and showing.
Shop One K CCS Parts
Top panels, front shields, rails and refit liners
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One K CCS Front Shield - Chrome
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One K CCS Vent Stripe Rail - Rose Gold
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One K CCS Top Panel - Celestial Black
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One K Crystal CCS Front Shield - Black Matte White
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One K CCS MIPS Refit Liner
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One K CCS Front Shield - Rose Gold
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One K CCS Vent Stripe Rail - Chrome
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One K CCS Vent Stripe Rail - Burgundy Matte
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One K CCS Top Panel - Black Matte
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One K Defender Refit Liner
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One K CCS Accessory Rail - Navy Crystal Rail
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One K CCS Accessory Rail - Crystal Rail
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One K CCS Accessory Rail - Black Crystal Rail
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One K CCS Top Panel - Navy Galaxy
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One K CCS Top Panel - Black Galaxy
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One K CCS Top Panel - Black Diamond Stone
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One K CCS Top Panel - Celestial Blue
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One K Designer CCS Top Panel - Blue Diamond Stone
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One K Designer CCS Top Panel - Black Horsehead
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One K Designer CCS Top Panel - Matte White Stars Black
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One K Designer CCS Top Panel - Gloss White Stars Black
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One K Designer CCS Top Panel - Gold Stars Black
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One K Designer CCS Top Panel - Black Snake
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One K CCS MIPS JR Refit Liner
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One K CCS Front Shield - White Gloss
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One K CCS Front Shield - Royal Blue Matte
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One K CCS Front Shield - Royal Blue Gloss
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One K CCS Front Shield - Rose Gloss
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One K CCS Front Shield - Red Gloss
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One K CCS Front Shield - Purple Matte
One K makes riding helmets that pair a comfortable fit with a look you can make your own. Shop the Mips CCS Helmet, the Avance Mips CCS and Defender Mips CCS, the classic Defender in matte, stripe and suede, the Avance Wide Brim and junior helmets, plus Custom Color System top panels, front shields, rails, refit liners and the Klick n Go Sunshield. Premium brands for less, with new deals every day.
Read more
One K Mips helmets
One K's Mips CCS helmets add a low-friction layer designed to reduce rotational motion from angled impacts. Learn how to choose and fit a helmet in our Helmet Center.
One K sizing
One K helmets come in regular and long oval shells, and refit liners fine-tune the fit. Our Helmet Buyer's Guide explains how to measure.
One K for the show ring
The Defender Suede and the stripe helmets are popular show helmets. See what to wear in each ring in our Competition Apparel Guide.
One K pairs a comfortable fit with a look you can make your own. Our three picks:
One K Mips CCS Helmet
Mips in a matte composite shell, with a washable quick-dry liner and Custom Color System parts to change the look.
One K Mips CCS Avance Wide Brim Helmet
The Avance's sun-shading wide brim with Mips and Custom Color System parts.
One K Defender Helmet
The classic One K: a composite shell, seven vents with stainless steel mesh and a padded, suede-lined harness.
★★★★★
Love this helmet. It is honestly the most comfortable helmet I own (yes I own several). I bought it to be my competition helmet but have been riding in it at home and it fits well and feels great.
Verified buyer · CA ★★★★★
I have a big oval head and this is the first MIPs helmet that I’ve been able to forget I’m wearing. It fits so well, is so comfortable, and actually fits - no more forehead indents. I measured at 57mm but the medium fits me perfectly.
Verified buyer · TX ★★★★★
I love this helmet! Just purchased my second.
Verified buyer · PA ★★★★★
Returned for a smaller size but the helmet feels good; it’s light and nicely padded. The other MIPs helmets I’ve tried have had dial-fit and felt like bike helmets.
Verified buyer · TX
Who is One K?
One K makes English riding helmets: Mips CCS helmets with interchangeable color parts, the Defender, the Avance Wide Brim and junior helmets. The company is based in Scranton, Pennsylvania.
What is Mips?
Mips (Multi-directional Impact Protection System) was founded in 1996 by a neurosurgeon and a researcher from the Royal Institute of Technology in Sweden. A low-friction layer inside the helmet allows a small sliding motion that is designed to reduce rotational motion transmitted to the brain from angled impacts.
What is the One K Custom Color System?
CCS lets you change three parts of a One K CCS helmet: the front shield, the vent stripe rail and the top panel. One K says the parts can be combined into over 2,100 looks.
Should I choose a regular or long oval One K?
Long oval shells are slightly narrower side to side and longer front to back. If a regular helmet presses on your forehead and the back of your head but feels loose at the sides, try the long oval. Check the size chart on each helmet's page.
Can I change the fit of my One K helmet?
Yes. Refit liners change the fit of a shell: for example, a Medium shell with a Small or X-Small liner fits as a Small or X-Small. They are useful for growing children, shared helmets and riders who wear their hair differently for schooling and showing.
Does One K make helmets for kids?
Yes. The Kids' Defender Jr and the Mips Jr CCS are sized for younger riders. The Defender Jr has a smaller internal diameter, a thicker padded liner and a chin strap 15 mm shorter than adult sizes.
