The One K Defender Refit Replacement Helmet Liner allows riders to customize the fit of their One K helmet with ease. Ideal for growing children, shared helmets, or riders who change their hairstyle between schooling and show, these liners provide flexible sizing without needing a new helmet.

Three base shells—Medium, Large, and X‑Large—accommodate multiple liner sizes. A Medium shell can be converted to Small or X‑Small by swapping liners, while an X‑Large shell can be adjusted to XX‑Large. The Large shell fits only a Large liner, though keeping an extra liner on hand is useful for freshness and convenience. This modular system ensures a precise, comfortable fit tailored to each rider’s needs.

Key Features:

• Flexible sizing system — swap liners to adjust helmet fit across multiple sizes
• Shell‑based fit options — Medium and X‑Large shells accommodate additional liner sizes
• Ideal for shared use — perfect for growing riders or helmets used for both schooling and show