Defender One Tour Forest Green Mountain Bike Helmet - Forest Green / M (55-58CM)

To ensure optimal comfort and protection, please refer to the Dotphy size guide. We recommend trying on the product whenever possible. Each helmet product page includes internal dimension ratios to help you better match your head shape.

MTB Helmet Size Chart

Fit Tip: MTB Helmet

MTB helmets should fit snugly for technical trails and bumpy terrain. Make sure the helmet sits low and level, with minimal movement when shaken. Choose a size that provides firm coverage without pressure.

Road Helmet Size Chart

Fit Tip: Road Helmet

Road cycling helmets prioritize aerodynamics and lightweight feel. The helmet should sit close to the head without gaps, secure during head movement, and allow airflow for long-distance comfort.

Full-Face MTB Helmet Size Chart

Fit Tip: Full-Face Helmet

Full-face helmets should fit snugly around the cheeks and crown without gaps. Ensure the chin bar feels secure but not tight, and there’s no excessive movement during head turns or jumps.

Snow Helmet Size Chart

Fit Tip: Snow Helmet

Snow helmets need room for warmth and goggle compatibility. Make sure the fit is not too tight when worn with a balaclava or beanie. The helmet should sit comfortably above the eyebrows and align with goggle straps.

Asian Fit Note

Dotphy helmets are developed with head shape diversity in mind. Asian users typically have a rounder head shape and shorter front-to-back ratio compared to European users. Each helmet product page includes internal fit dimensions to help ensure the best match for your head shape. If you fall between sizes, prioritize internal width and frontal coverage for comfort.

How to Measure Your Head

1. Use a soft measuring tape or string.
2. Wrap it around your head about 2 cm above the eyebrows and ears, keeping it level.
3. Check your measurement in centimeters and compare it to the chart above.

Tip: Try on the helmet with the fit system loosened first. The shell should rest evenly around your head, with adjustability to tighten securely without discomfort.

Snow Goggle Size Chart

Choose the right goggle frame for your face size and helmet fit. Goggles should create a full seal around your eyes without pressure points or gaps.

Small Frame

Best for youth and adults with narrow or smaller faces.

Medium Frame

The most common size for adults. Unisex fit with balanced field of view and comfort.

Large / Oversized Frame

Offers maximum peripheral vision, ideal for broader faces. Ensure helmet compatibility before purchase.

OTG (Over-the-Glasses) Goggles

Designed for use over prescription eyewear. These frames offer extra internal space for both glasses and airflow.

Note: Size and fit recommendations are provided for guidance only. Actual fit may vary by model. Please refer to the individual product pages for specific internal sizing details.