Table 20.1 shows average ear canal length (in mm) for healthy full-term babies starting at 1 month through 24 months.6 The shorter overall length of the infant ear canal (14 mm) requires special attention when placing an otoblock for an earmold impression. Fig. 20.1 shows the placement of a small otoblock (~ 3 mm) about 5 mm from the tympanic membrane. That leaves only 6 mm for the impression material, which is equivalent to the width of a paper clip at the narrow end.