This is a multi-function armband, but to be exact, it shall be called a multi-function mobile phone holder.
This set includes a silical holder and 2 different length velcros. So it can be fixed on cylinders of different diameters. Your cell phone can be fixed as armband, waist bag, it can be fixed on mineral water bottle, it can be fixed on the steering wheel as navigation, it can be fixed on the back side of car seat...
The silical holder is anti-slip and elastic, so there is no need to worry about the size of your phone.
The product also comes with a small bag for storing the product. When it is used as a waist bag, this bad can be attached to the velcro to store keys, earphones etc.