Male contraceptives are methods of preventing pregnancy that primarily involve the male physiology. The most common kinds of male contraception include condoms, withdrawal / pulling out, outercourse, and  vasectomy. In domestic animals, castration is commonly used for contraception. Other forms of male contraception are in various stages of research and development. These include methods like RISUG/VasalGel (which has completed a small phase II clinical trial in humans in India) and ultrasound (with results so far obtained in experimental animals).