[COOLING HELMET LINER]: ROCKBROS Cycling Helmet Liner Cap is made of high-quality ice silk material and breathable mesh surface, which has nice quick drying and sweat absorbing performance, bringing you a comfortable wearing experience in hot summer.[LIGHTWEIGHT & PORTABLE]: This beanie cap is thin and small enough to placed in your pockets or store on your bike bag conveniently for those moments where you need.[SUN PROTECTION]: UPF 50 Cooling Skull Cap can resist more than 98% of harmful UVA and UVB rays, effectively protecting your skin from sunburn in summer[WIDE APPLICATION]: The cycling skull cap can be worn as a helmet liner or hard hat, it’s also perfect for most indoor or outdoor activities such as cycling, running, workout, motorcycle,walking, hiking, jogging, gym, tennis, football and etc.[ONE SIZE FITS ALL]: Our helmet liner is made of highly elastic material, easy to put on and take off, suitable for head circumferences from 50cm/20.47″ to 64cm/25.19″, so it fits most men and women