Fitting and adjustment

The OneK helmets are available in 3 shell sizes. By using the OneK foam liners which are available from XXXS to XXL you can achieve the perfect fit! The liners are available as standard fit and with an oval shape to meet the needs of riders with an oval head shape. This system also allows the helmet to grow with the young rider.
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HELMETS SIZE CHART

Helmet Size Centimeter Measurement Hat Size
X-Small 51 - 52 cm 6 3/8 - 6 1/2
Small 53 - 54 cm 6 5/8 - 6 3/4
Medium 55 - 56 cm 6 7/8 - 7
Large 57 - 58 cm 7 1/8 - 7 1/4
X-Large 59 - 60 cm 7 3/8 - 7 1/2
XX-Large 61 - 62 cm 7 5/8 - 7 3/4

Junior HELMETS SIZE CHART

Helmet Size Centimeter Measurement Hat Size
X-Small 47 - 48 cm 5 7/8 - 6
Small 49 - 50 cm 6 1/8 - 6 1/4
Medium 51 - 52 cm 6 3/8 - 6 1/2

One K™ liners

The OneK helmets are available in 3 shell sizes. By using the OneK foam liners which are available from XXXS to XXL you can achieve the perfect fit! The liners are available as standard fit and with an oval shape to meet the needs of riders with an oval head shape. This system also allows the helmet to grow with the young rider.
One K Helmet Liners
Instantly Refresh Helmet with a Replacement Liner!

Helmet LINERS CONVERSION chart

Stock Helmet Can change helmet to: By replacing with liner sized:
X-Small
(6 3/8 - 6 1/2")
Small
Medium
Small
Medium
Small
(6 5/8 - 6 3/4")
X-Small
Medium
X-Small
Medium
Medium
(6 7/8 - 7")
X-Small
Small
X-Small
Small
Large
(7 1/8 - 7 1/4")
X-Large X-Large
X-Large
(7 3/8 - 1 1/2")
XX-Large XX-Large
XX-Large
(7 5/8 - 7 3/4")
X-Large X-Large

JUNIOR Helmet LINERS CONVERSION chart

Stock Helmet Can change helmet to: By replacing with liner sized:
X-Small Junior
(5 7/8 - 6")
Small Junior
Medium Junior
Small Junior
Medium Junior
Small Junior
(6 1/8 - 6 1/4")
X-Small Junior
Medium Junior
X-Small Junior
Medium Junior
Medium
(6 3/8 - 6 1/2")
X-Small Junior
Small Junior
X-Small Junior
Small Junior
X
×