A barrier contraceptive. The male condom, usually rubber, is a sheath that fits over the man's penis to prevent sperm from entering the vagina. The male condom is more effective than most other contraceptives in preventing transmission of sexually transmitted diseases. A female condom is a bit like the reverse of a male condom. A rubber cup is inserted into the vagina with a portion of the condom remaining outside of the vagina, sometimes covering the labia.