HJC I 31 SF MET BLUE
The i31 is HJC's modern open-face jet — a CAD-developed APC shell with a proper face shield and an internal sun visor behind it, so it covers a commute as... Read More
The i31 is HJC's modern open-face jet — a CAD-developed APC shell with a proper face shield and an internal sun visor behind it, so it covers a commute as readily as a Sunday cruise.
The HJ-43 shield swaps with the RapidFire system, is Pinlock-ready and blocks 99% of UV; the HJ-V12 sun shield is anti-fog and anti-scratch coated. The MultiCool interior wicks, dries fast and lifts out for washing, and the shell has grooves cut for glasses.
Features
- DOT FMVSS 218 certified
- APC (Advanced Polycarbonate Compound) shell, CAD-developed injection moulding
- HJ-43 face shield, Pinlock-ready, 99% UV protection, RapidFire tool-less shield change
- HJ-V12 internal drop-down sun shield, anti-fog and anti-scratch coated
- ACS Advanced Channeling Ventilation — 1 intake, 2 exhausts
- MultiCool moisture-wicking quick-dry interior, removable and washable
- Eyeglass grooves
Specs
- Certification: DOT FMVSS 218
- Shell: APC (Advanced Polycarbonate Compound)
- Shield: HJ-43, Pinlock-ready, RapidFire change system
- Sun shield: HJ-V12 internal drop-down
- Interior: MultiCool, removable/washable
How to measure
Wrap a cloth tape measure horizontally around the fullest part of your head, about 1 inch (2.5 cm) above the eyebrows. Repeat a few times and use the largest measurement. The chart is a starting point — always try the helmet on for final fit.
HJC size chart
| Size | Head circumference (cm) | Head circumference (inches) | Hat size |
|---|---|---|---|
| 3XS | 50-51 | 19 3/4 - 20 1/8 | 6 1/4 - 6 3/8 |
| 2XS | 52-53 | 20 1/2 - 20 7/8 | 6 1/2 - 6 5/8 |
| XS | 54-55 | 21 1/4 - 21 5/8 | 6 3/4 - 6 7/8 |
| S | 55-56 | 21 5/8 - 22 | 6 7/8 - 7 |
| M | 57-58 | 22 3/8 - 22 7/8 | 7 1/8 - 7 1/4 |
| L | 58-59 | 22 7/8 - 23 1/4 | 7 1/4 - 7 3/8 |
| XL | 60-61 | 23 5/8 - 24 | 7 1/2 - 7 5/8 |
| 2XL | 62-63 | 24 3/8 - 24 3/4 | 7 3/4 - 7 7/8 |
| 3XL | 64-65 | 25 1/8 - 25 1/2 | 8 - 8 1/8 |
| 4XL | 66-67 | 26 - 26 3/8 | 8 1/4 - 8 3/8 |
| 5XL | 68-69 | 26 3/4 - 27 1/8 | 8 1/2 - 8 5/8 |
Youth sizes
| Size | Head circumference (cm) | Head circumference (inches) |
|---|---|---|
| YS | 48-49 | 18 7/8 - 19 1/4 |
| YM | 50-51 | 19 5/8 - 20 1/8 |
| YL | 52-53 | 20 1/2 - 20 7/8 |
One official HJC chart covers all models (full-face, modular, open-face, half); size availability varies per model. cm values are canonical (verified on both official US and EU HJC sites); inch values follow the mathematically consistent EU print where the US page conflicts with its own cm column (M and L rows). Note: many retailers still publish HJC's LEGACY chart (XS 53-54 … 3XL 65-66), which disagrees with the current official chart — do not mix them. Youth chart is the official Y10 chart (EU site).
Manufacturer sizing data · verified July 8, 2026