Skip to footer
This Item Ships For Free!
Shop All One K Helmets

One K Defender Series Riding Helmet

5.0
1 Review
This Item Ships For Free!
Shop All One K Helmets

One K Defender Series Riding Helmet

5.0
1 Review
$289.95
One K Defender Matte Black XS Reg
In Stock: 1
Price: $289.95
  • Color: Black Stock # 468259BKMATXS
  • Helmet Size: XS
  • Helmet Shape: Reg
One K Defender Matte Black SM Reg
In Stock: 1
Price: $289.95
  • Color: Black Stock # 468259BKMATSML
  • Helmet Size: SM
  • Helmet Shape: Reg
One K Defender Matte Black MD Reg
In Stock: 2
Price: $289.95
  • Color: Black Stock # 468259BKMATMED
  • Helmet Size: MD
  • Helmet Shape: Reg
One K Defender Matte Black LG Reg
In Stock: 3
Price: $289.95
  • Color: Black Stock # 468259BKMATLRG
  • Helmet Size: LG
  • Helmet Shape: Reg
One K Defender Matte Black XL Reg
In Stock: 2
Price: $289.95
  • Color: Black Stock # 468259BKMATXL
  • Helmet Size: XL
  • Helmet Shape: Reg
One K Defender Matte Black XS Long Oval
In Stock: 2
Price: $289.95
  • Color: Black Stock # 468259BKMATXSL
  • Helmet Size: XS
  • Helmet Shape: Long Oval
One K Defender Matte Black SM Long Oval
In Stock: 1
Price: $289.95
  • Color: Black Stock # 468259BKMATSMLL
  • Helmet Size: SM
  • Helmet Shape: Long Oval
One K Defender Matte Black MD Long Oval
In Stock: 1
Price: $289.95
  • Color: Black Stock # 468259BKMATMEDL
  • Helmet Size: MD
  • Helmet Shape: Long Oval
One K Defender Matte Black LG Long Oval
In Stock: 3
Price: $289.95
  • Color: Black Stock # 468259BKMATLRGL
  • Helmet Size: LG
  • Helmet Shape: Long Oval
One K Defender Matte Black XL Long Oval
In Stock: 1
Price: $289.95
  • Color: Black Stock # 468259BKMATXLGL
  • Helmet Size: XL
  • Helmet Shape: Long Oval
One K Defender Matte Navy SM Reg
In Stock: 1
Price: $289.95
  • Color: Navy Stock # 468259NYMATSML
  • Helmet Size: SM
  • Helmet Shape: Reg

Riding Warehouse wants you to be completely satisfied with your purchase. Items can be returned at any point in new condition within 365 days of the original invoice date.

Products returned in new, store-bought condition are eligible for exchange, refund, or Riding Warehouse store credit for the full value of your purchase.

Products returned that are unable to be returned to stock are eligible to receive Riding Warehouse store credit for the full value of your purchase. Please note that while we want you to be happy with your purchases, an excessive number of used returns within a twelve-month period may limit your eligibility for store credit.

Products returned beyond 365 days from the original invoice date may be eligible for partial store credit at the sole discretion of Riding Warehouse.

Original shipping charges are non-refundable.

Overview

Key Features

Removable LinerRemovable Liner
Customizable OptionsCustomizable Options
Universal ShapeUniversal Shape

Key Features

  • Wide BrimWide Brim

    Wider than traditional helmet visors, the front and outward extension protects riders from sun damage and reduces glare. Size may vary by brand or helmet style.

  • Dial AdjustabilityDial Adjustability

    Featuring an adjustable dial at the back of the helmet, these can either be tightened or loosened to correct minor helmet fitting issues and create the perfect fit.

  • Removable LinerRemovable Liner

    These helmets have liners that can be removed for easy cleaning or to adjust fit.

  • Customizable OptionsCustomizable Options

    These helmets allow you to personalize your helmet with front, back, or top inserts in numerous colors and patterns that show off your individual style.

  • Round ShapeRound Shape

    These helmets are the most comfortable option for riders with a rounder-shaped head. Click here to determine your head shape.

  • Oval ShapeOval Shape

    Riders with an oval-shaped head will feel most comfortable in these helmets. Click here to determine your head shape.

  • Universal ShapeUniversal Shape

    These helmets can fit any head shape through changing of liners, dial adjustability, or various shell sizes so you can find the right fit for your head's size and shape.

Safety Measures

ASTM/SEI CertifiedASTM/SEI Certified

Safety Measures

  • ASTM/SEI CertifiedASTM/SEI Certified

    The American Society for Testing and Materials (ASTM) writes widely known safety standards, then an independent testing laboratory called the Safety Equipment Institute (SEI) ensures that manufacturers design helmets that are up to par. The ASTM/SEI testing standard requires impact and retention tests, as well as a visor test to make sure that the visor breaks away or flexes without injuring the face.

  • European CertifiedEuropean Certified

    European standards are put together by a committee comprised of representatives from countries in the EU. In addition to impact, retention, and visor tests, these safety standards demand that helmets withstand penetration and crushing. The inclusion of the latter two tests is thought to produce safer helmets than those only certified to ASTM standards by SEI.

  • SNELL CertifiedSNELL Certified

    The Snell Foundation uses what is considered the most demanding testing procedure for riding helmets. Their tests include all aspects of the other certifications but with more stringent standards. Snell drops the helmets from a greater height during the impact test onto a variety of differently-shaped anvils, has the highest crush resistance rating, and ensures the helmet offers sufficient head coverage without sacrificing the rider's field of vision.

  • MIPSMIPS

    MIPS, or Multi-Directional Impact Protection System, is an additional layer embedded in some helmets to reduce strain on the brain upon a fall. When the helmet makes contact with a surface, the low-friction MIPS layer allows the head to move 10 to 15 mm in all directions to dissipate impact on the brain.

  • ERT FoamERT Foam

    ERT, or Energy Reduction Technology, consists of soft polymer pads incorporated into the helmet design that mitigates rotational and linear impact. With the motto "Softer is Safer", ERT works immediately and is most effective with lower-impact falls.

Enter the show ring with sophisticated style and undeniable comfort with the One K Defender Riding Helmet. A sleek injection-molded outer shell with discreet stainless steel ventilation panels boasts a professional finish to appeal to even the most discerning of fashion-forward equestrians. Modern technology ensures maximum safety while unique user-friendly features provide optimal comfort, durability, and ease of use.

With a washable, quick-dry, anti-microbial lining system, the One K Defender stands true to its name to fight moisture build-up and prevent odor and discomfort. A unique padded harness with a soft synthetic suede lining features Velcro adjustment options for a truly customized fit while the Fastex® chin buckle allows one-handed ease of use!

Details

  • Polycarbonate/Advanced ABS Composite Outer Shell
  • Washable, Quick-Dry Lining with Anti-Microbial Protection
  • Sleek, Stainless Steel Mesh Ventilation Channels
  • Comfort Padded Harness with Soft Synthetic Suede Lining
  • Customizable Velcro-Adjustment Chin Strap with Fastex® Buckle
  • Painted Matte Finish for a Sleek & Professional Appeal
  • ASTM F1163-15/SEI Certified 

Additional Information

One K offers a 3-year replacement policy if your helmet is in an accident. See information about this policy here.

Sizing

Please Note: Check the sizing chart and measure, as these helmets may run small.

Size Head Circumference Cap Size
XS 51 - 52 cm 6 3/8 - 6 1/2
SM 53 - 54 cm 6 5/8 - 6 3/4
MD 55 - 56 cm 6 7/8 - 7
LG 57 - 58 cm 7 1/8 - 7 1/4
XL 59 - 60 cm 7 3/8 - 7 1/2
XXL 61 - 62cm 7 5/8 - 7 3/4

See how a helmet should correctly fit with Kim Gentry in this helpful sizing video

Videos

Customer Reviews

5.0 out of 5
1 Customer Review
5 out of 5 Stars
Would Recommend
Comfortable helmetThis helmet fits well and is very comfortable since it is available in the oval shape. The padding is great and the harness feels secure. I also like the ventilation- you can actually feel the air move through it. The best helmet is the one you don't think about once you put it on and I am very happy with this one!

Previous Feedback

The customer comments shown below were gathered using our previous feedback system. While these comments are not used in the calculation of the star rating for this product, they are displayed to help provide you with the most complete customer feedback available.

Comments: THE BEST HELMET EVER! I love the fit on these helmets - it's perfect. They are comfortable and fit snugly. Will be my go to for now on and you can't beat Riding Warehouse's shipping! 
From: Alexandra - San Jose, California, USA 

Comments: I've had many helmets over the years, and the One K has by far been my favorite. The sleek shell of the defender not only looks good, but is comfortable, and the removable inserts make it a breeze to wash or to change the fit of the helmet for when I have my hair in a ponytail. The cherry on top is that it is budget friendly!  
From: Cenn - St. Charles, Illinois, USA 

Comments: Beautiful, elegant style and wonderful fit. I have a very uneven shaped head and subsequently tried on numerous helmets to no avail. Fortunately this helmet fits like a glove. I love the comfort of the foam in the liner and the ability to remove, machine wash, and replace the liner. I also love that I can simply move up to a larger size liner when I put my hair in a net/grow my hair out. RW customer service was excellent and shipping across the country was so fast. *Almost* want to buy another one in the rose gold! 
From: Janice- Texas, USA 

Comments: I put this helmet on, and I swear I heard angels singing. I was a bit worried about S/M/L sizing, as I typically wear either a 6 3/4 or a 6 7/8, but I ordered a medium long oval and hoped for the best. It is PERFECTION. I can turn my head upside down without fastening the harness and the helmet does not fall off, yet I just walked around my house for 2 hours and there's no hint of a pressure spot on my forehead or a headache, which is my usual problem trying to make round-ish helmets fit my oval head. I don't love the angle of the chin harness - it seems to come too far forward, almost jabbing into my chin, but it seems like that will stretch and soften with time. Thanks to RW's generous return policy, I tried and returned 2 sizes of the IRH Elite (6 7/8 was too big, but 6 3/4 seemed perched) and the CO Pro II. Glad the 4th (eek) time was finally the charm. Thank you for carrying the long oval shape, and for not cutting me off as a customer after so many returns ;)  
From: Jennifer - Pittsburg, Pennsylvania, USA 

Comments: This helmet gets a lot of compliments. I just took a fall wearing this helmet and while I'm pretty well bruised and the helmet needs to be replaced I can say the my head was well protected.  
From: Yvonne - Rochester, New York, USA 

Comments: Fits great and feels very secure. I keep a spare liner to switch out every few rides. It stays comfortable for long rides and never makes my head hurt. I don't notice a huge difference with keeping my head cooler, though.
From: Abigail - Petaluma, California, USA

Comments: Ah-mazing helmet! Worth every penny. Fits snugly enough - it feels secure but doesn't smother you. Looks really good too!
From: Rebekah - Turlock, California, USA

Comments: Super profile with a beautiful color. The first helmet I ordered had issues with the liner, but Riding Warehouse promptly exchanged it for me. Couldn't be happier with this purchase! 
From: Dani- Milwaukee, Wisconsin, USA 

Comments: Best fitting helmet and at a reasonable price! Great lightweight helmet that actually fits my tiny head. Vented and comfortable even with our hot, humid summers. The lining can be taken out and washed. Love this helmet. 
From: Shelton- Charleston, South Carolina, USA

Comments: It took me a long time to find a helmet that I liked the look of, and I am so glad I found the One K... I LOVE it...it is super easy to keep clean too!!
From: Stephani - Anchorage, AK, U.S.A.

Comments: Love the profile and is the first helmet that actually fits my small head! Service was excellent and arrived as scheduled per tracking! Will definitely shop here again! Thx!
From: Carole - Peach Bottom, PA, U.S.A.

Back to Top