One size fits all: This LED bracelet measures 35 x 2.5 cm and is suitable for both adults and children, simply by sliding it into another position such as the wrist, ankle or arm. You can adjust the buckle to fit different sizes. Ultra High Visibility:- This light up wristband has 3 working modes: always on, fast flashing, slow flashing. Lights up with LED and TPU driver tube in thin nylon fabric, providing 360 ultra high visibility during twilight and nighttime activities. Lightweight and easy to carry: just wear the reflective strip LED (28g/piece). to your arm and secure it with the release buckle. It is very lightweight that you won't feel uncomfortable when running, cycling, etc. 4 Pack LED Wristbands: You will receive 4 LED wristbands in one package. You can carry it in your arms or share it with your friends or family. Powered by 2 CR2032 batteries which can work for about 40-60 hours. When the battery is empty, you can replace it with a new one.