To select the most appropriate receiver cable length:
Firmly place the Measurement Tool horizontally over the ear with the short edge of the earhook facing toward the back of the head.
Use the Measurement Tool to select receiver cable length.
Choose the receiver cable length that is closest to the mark at the top of the opening of the ear canal. If the canal opening falls between the lines, select the shorter tubing for length. For the ear in picture above, a size 3 or 4 receiver cable would be selected.