Adjustable Helmet Size: VG110 model bike helmet is suitable for adult men and women, 3 sizes available, size M: 21.3-22.8 inch (54-58 cm); size L: 22.4-24 inch (57-61 cm); size XL: 23.2-24.8 inch (59-63 cm). It is easy to adjust the bicycle helmet size with hand. Our bicycle helmet will give you a comfortable and happy cycling trip. Cool and Lightweight Cycling Helmet: Our bike helmet is designed with 21 breathable vents, the cooling vents can move airflow over your head to stay cool and dry. This cycling helmet only 310g (0.68 lb) will not cause any burden to the rider's head during cycling. Impact Resistance: Our bike helmet is made of high-density PC shell and EPS foam, with durable hard shell and soft pad can absorb the pressure caused by external impact. Our bicycle helmet provides better protection when road cycling or mountain biking, greatly helping to decrease and buffer the impact. Magnetic Helmet Goggles and Visor: This bike helmet with visor and goggles, it is an ideal bike helmet for mountain bike and road bike cycling. You can put the goggles and visor together, not only can protect your eyes from sunlight, but also can protect your face against the sand and wind. It also wont interfere with wearing your own glasses. Bright Helmet Rear Light: Our bike helmet with light in the back, it has 3 flashing mode light- steady, slow flashing and fast flashing. It is necessary to equip taillights for night cycling, it will help riders behind you clearly recognize your direction and warning the car.