||A suitable speculum is required to hold open the outermost portion of the cartilaginous meatus and to allow the passage of both light and instruments.
As a general principle, the largest aural speculum which can be comfortably introduced into the meatus should be used.
The appropriate size for adults is from 4 to 7 mm in diameter; for children it is approximately 3 mm and for infants a speculum as small as 2 mm may have to be used.
Because the normal external canal is oval rather than circular in cross‑section, oval specula tend to fit more easily and snugly into the canal than those which are perfectly round.
With the patient seated, an oval speculum is inserted with its widest diameter in the vertical axis.
The ideal speculum is smooth and has a non‑reflecting dark inner surface. Specula made either of metal (expensive) or synthetic plastic materials (inexpensive) are available.