The diaphragm is a mechanical barrier between the vagina and the cervical canal. Diaphragms are circular rings ranging from 50-105 mm in diameter, which are designed to fit in the vaginal cul-de-sac and cover the cervix. Although the designs vary, the arcing spring version is probably the easiest to use for most women. A contraceptive jelly or cream should be placed on the cervical side of the diaphragm before insertion, since the device is ineffective without it. This medication also serves as a lubricant for insertion of the device. Additional jelly should be introduced into the vagina on and around the diaphragm after it is securely in place. When the diaphragm is of proper size (as determined by pelvic examination and trial with fitting rings) and is used according to directions, its failure rate is 2-20 pregnancies per 100 women per year of exposure. The diaphragm has the disadvantages of requiring fitting by a physician or a trained paramedical person and the necessity for anticipating the need for contraception. Failures may result from improper fitting or placement and dislodgment of the diaphragm during intercourse. As with condoms, diaphragms also offer some protection against STDs. The only side effects are vaginal wall irritation, usually with initial use or if the device fits too tightly, and an increased risk of urinary tract infections.