The patch is a thin, beige-colored device that adheres to a woman's skin like a band-aid for a week at a time. After receiving a prescription for the patch, a woman will apply the sticky part to the skin of her buttocks, stomach, upper arm, or upper torso. On the same day a week later, the patch should be removed and replaced. This continues for three weeks, with a one week break during which a woman has her period. This device works in the same manner as Depo-Provera. With correct use, the patch is more than 99 percent effective and is usually quite affordable at about $30 U.S dollars per month. However, women who are over 180 pounds or who have a body mass index greater than 30 may experience less success with this method. In addition, the patch is not recommended for people who take certain medications, like those used to treat seizures. In general, both the shot and the patch are quite effective at preventing pregnancy; however neither offers protection against sexually transmitted diseases. For this reason, some women use condoms to reduce STD transmission and for back-up pregnancy prevention.