Protective mountain bike helmet BELL 4FORTY AIR size M (55–59 cm) Matte White Black

BELL 4FORTY AIR size M (55–59 cm) in Matte White Black is a protective mountain bike helmet engineered for trail and all‑mountain riding. The helmet combines a ventilated shell design with impact protection features to provide coverage appropriate for off‑road cycling. Its adjustable fit system allows secure positioning on medium head sizes, while the matte two‑tone finish offers understated styling suitable for everyday training and trail sessions.

Advantages

The helmet delivers a balance of ventilation and protection through strategically placed vents and a molded shell construction that helps manage airflow and distribute impact forces. An adjustable retention system enables a customized, stable fit across the 55–59 cm range. The extended rear coverage typical of trail helmets offers extra protection for the occipital area without significantly increasing weight. Materials and build quality are intended for regular use in mountain biking conditions.

Suitable for

• Trail riding and singletrack
• All‑mountain and enduro training
• Daily off‑road training sessions
• Commuting on mixed surface routes

Key specifications

• Size range: medium (55–59 cm)
• Style: mountain bike / trail helmet
• Finish: matte white and black two‑tone
• Ventilation: multiple intake and exhaust vents for airflow
• Fit system: adjustable retention for secure positioning
• Coverage: extended rear/head coverage for off‑road protection

How to use

Place the helmet level on the head so the front rim sits just above the eyebrows. Adjust the retention system and side straps to achieve a snug, stable fit without excessive pressure. Ensure the chin strap is buckled and adjusted so two fingers fit between the strap and the chin. Check ventilation openings are unobstructed and that the helmet sits evenly during movement. Inspect the helmet regularly for signs of damage and replace it following any significant impact.

Usage recommendations

Use the BELL 4FORTY AIR for trail and all‑mountain activities where increased coverage and ventilation are required. Match the medium size to a head circumference of 55–59 cm, and replace the helmet after a major crash or when structural wear is observed. Clean the helmet with mild soap and water; avoid solvents or strong cleaners that can degrade materials.