Keep the fitting instructions beside the helmet record
Keep the exact helmet chart, measured head circumference and fitting instructions together without treating a size label as a fit guarantee.
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Use the chart for the helmet you are considering
Begin a helmet-fit enquiry with the exact model and the manufacturer's own measuring instructions. Record the measurement unit and date beside the result. A size label from a different helmet is a poor substitute because the new product may use a different chart or shape. If you are unsure where or how to measure, obtain help from the seller or a qualified fitter instead of inventing a method. The purpose of the note is to support a fitting discussion, not to choose a helmet solely from a number.
Bell Stratus Mips US size chart ? ACCC bicycle helmet supply standard ? NSW helmet guidance ?
Notice where the chart overlaps
Bell's US Stratus Mips example lists small at 52–56 cm and medium at 55–59 cm, with large at 58–62 cm. The ranges overlap. An illustrative 55 cm measurement appears in the first two ranges, so the chart alone does not select a unique answer. Do not automatically choose the smaller or larger option from that overlap. Follow the exact model's instructions and assess the actual fit with appropriate help. This overseas chart is an explanation of how to read ranges, not an Australian product approval or a recommendation to purchase that version.
Save the instructions with the measurement
The ACCC's helmet overview says fitting and positioning instructions should accompany the helmet. Retain those instructions, or a manufacturer copy that matches the exact version, alongside the measurement record. Write down the model and size actually tried rather than only the one initially considered online. Keep any retailer advice in context: who provided it, which helmet they saw and what remained unresolved. A general comment about head size should not be transformed into a claim that the retention system, position and fit have all been checked.
Keep other questions out of the size field
A size chart does not answer whether a helmet is damaged, suitable for an intended use or allowed under the relevant road rules. NSW's guidance addresses fit, fastening and condition separately. Use the applicable guidance for your own location, and verify the exact item rather than borrowing a statement about another market. The photographs here are archive views of different helmets, with no inspection or fit assessment by this publication. Their colours and shapes are visual context only, and should not be used to infer the dimensions or condition of the product you are considering.
Make the final purchase record specific
After resolving the fitting questions, keep the final model, size, supplied instructions and seller details together. Check the delivered item against that record before discarding packaging. If the fit differs from what was expected, contact the seller rather than trying undocumented adjustments or accessories. Preserve the initial measurement as an observation, but do not let it override what the actual helmet and its instructions show. Revisit the fit when circumstances change and follow the manufacturer's advice. This record helps make a discussion precise; it cannot guarantee protection or replace an individual fitting assessment.
Open official model documentation ? Open official model documentation ? Open official model documentation ?
