Just as with modern hearing health devices intended for all-day wear, a driver of smaller volume in an in-ear wearable device can translate to smaller device size and thus to real improvement in fit and comfort. When considering the total volume needed for the driver in an in-ear wearable, the back volume becomes part of the equation. A good rule of thumb for Balanced Armature drivers is to provide additional back volume of at least 50% of the driver volume. For dynamic speakers it is typically 100%. Even without considering the back vent, a 6 mm dynamic speaker is nearly three times larger than Balanced Armature series RAB. With back venting factored in, the size ratio is even greater. Another point when considering the mechanical design is that with Balanced Armature drivers several port locations are available, giving greater flexibility in creating the layout.