"Matching a cap to a woman depends on multiple factors related to the angle, shape, and size of her cervix. Careful attention to the anatomy of the cervix is essential when fitting a woman for a cap. An assessment of the angle at which the cervix enters the vagina is crucial. If the cap’s rim can be touched by the penis during intercourse, then the potential for cap displacement is greatly increased. The length of the cervix must also be assessed. If the cervix is exceptionally long or short, it may be impossible to create a suction between the cervix and the cap’s interior."