BELL 4FORTY AIR MIPS mountain bike helmet, matte dark green/orange, size S (52–56 cm)

BELL 4FORTY AIR MIPS mountain bike helmet in matte dark green with orange accents is designed for trail and enduro riders seeking a balance of protection, ventilation and fit in a size S that fits head circumferences 52–56 cm. The helmet combines an impact-absorbing shell with integrated rotational protection technology, multiple airflow channels and an adjustable retention system while preserving a compact off‑road profile and a visor suitable for trail conditions.

Advantages

The helmet provides multi-directional impact mitigation through its built-in rotational protection system and an energy-absorbing shell construction for standard impact scenarios encountered in mountain biking. Ventilation channels and internal airflow design promote cooling during sustained efforts on climbs or technical sections. An adjustable retention system and padded interior enable a secure and customizable fit for the specified head size range, and the molded visor helps shield the face from sun, branches and trail spray.

Suitable for

• Trail riding and enduro stages where both protection and ventilation are required
• All-mountain training rides and long ascents where airflow matters
• Riders with head circumference between 52 and 56 cm seeking a size S fit
• Off‑road cycling in varied light and terrain conditions

When it may not be suitable

This helmet is optimized for trail and enduro use and may not be the best choice for riders who require a full-face helmet for downhill racing or extreme gravity disciplines. It also may be oversized for riders with head circumferences below 52 cm or too small for those above 56 cm — in such cases a different size or a different helmet model should be considered.

Key specifications

• Intended use: mountain bike (trail, enduro)
• Protection: impact-absorbing shell with integrated rotational protection system
• Shell finish: matte dark green with orange accents
• Size: S, fits head circumference 52–56 cm
• Ventilation: multiple airflow channels and internal ventilation design
• Fit system: adjustable retention and padded interior
• Visor: fixed/molded visor for off‑road use

How to use

Place the helmet squarely on the head so that the front edge sits approximately two finger-widths above the eyebrows. Adjust the retention system at the rear until the helmet feels snug but not tight, and secure the chin strap so it forms a V-shape under each ear with the buckle fastened comfortably under the chin. Confirm that the helmet does not shift significantly when you shake your head and that ventilation channels are unobstructed. Replace the helmet after any significant impact or according to the manufacturer’s recommended service life.

What to consider before purchase

• Measure head circumference to confirm a 52–56 cm (size S) fit
• Evaluate whether trail/enduro protection level matches your riding discipline
• Consider helmet weight and ventilation performance relative to ride duration and climate
• Check compatibility with eyewear and any communication or camera mounts you plan to use

Usage recommendations

Use the helmet for trail and enduro riding where a balance of ventilation and rotational impact protection is needed. Store it in a cool, dry place away from direct sunlight and chemicals. Inspect straps, retention system and shell regularly and replace the helmet after a crash or if visible damage appears.