Sizing - The most important factor in choosing the right size is the measurement around the widest part of your hand - as it needs to slip on and off over your hand. Although there is a little bit of stretch in the band, if you pull or tug on it too hard, or stretch it too far over your hand, it could break. This wristband is approx 202 mm or 8 inches - ideal for someone who measures up to 215 mm around the widest part of their hand. Would probably suit an adult (approx age 14+), although it is not appropriate if you have particularly large hands.