The adjustable elastic band is made of high quality materials and has a wide adjustment range, suitable for most arm sizes.Comfortable, sweat resistant, water resistant, durable and lightweight.This sports arm bag is used to store mobile phones, keys, lighters, earphones, credit cards, cash, keys and so on. Special earphone jack designed for enjoying musics conveniently when running.4 colors for choice.Great for gym, fitness, yoga, walking or outdoor activities such as running, cycling, fishing. Customized is available.