The long arm is referred to as the headband and it is manufactured to fit a wide variety of head sizes. The arm is angled inwards so that the sensor when fitted is making contact with the T8 location and not the plastic arm. The headband can be adjusted for users with bigger heads where the shipped headband is not comfortable. This can be done at home using a hairdryer. The arm is made from two separate layers of plastic but can be adjusted by warming the plastic with a hairdryer until it becomes pliable and allows you to slowly adjust the headband and they both need to be warm or it could separate while adjustment.