Impact resistance&Light weight: material is tough and durable PVC & PC, The helmet is made of lightweight material, it weights only 200g. Adjustable dimension:This helmet is specially designed for adults both men and women rider. It's suitable for 22'~25' head circumference. It goes with a standard size, equipped with the easy-use dial system and side straps make this helmet adjustable to different head size. Aerodynamic and ventilation design: The ventilation holes allow air to go through the cycle helmet,helping increase the speed and keep stay cool. Visor design:The special design of visor,you can enjoy cycling even in hot days,and the visor can be removed when you do not need it. The inner pads and chin pad are made of breathable material, soft and comfortable.They can be easily removed for wash and can be easily attached back to the helmet.Produktbeschreibung Features: 1.The liner pads and chin pad are soft and comfortable,absorb sweat,easily removed for washing. 2.There is a adjusting knob behind the helmet,helping to adjust the helmet circumference,make the helmet adjust to different head size.3.High-density imported PC case,improve the safety and protect you in emergent situation. 4.The helmet make of super light weight material,will not cause any burden to the rider during cycling. 5.This bike helmet suitable for city bike,road bike,electric bike,trekking,triathlon or mountain bike and etc. Method of measuring the head circumference: Use a tape measure to measure the circumference along the eyebrows to the back of the head. Take a few measurements and take an average.