A condom is a device most commonly used during sexual intercourse. It is put on a man’s erect penis and physically blocks ejaculated semen from entering the body of a sexual partner. Condoms are used to prevent pregnancy and transmission of sexually transmitted diseases (such as gonorrhea, syphilis, and HIV). Because condoms are waterproof, elastic, and durable, they are also used in a variety of use different applications. In the modern age, condoms are most often made from latex, but some are made from other materials such as polyurethane, or lamb intestine. A female condom is also available, most often made of polyurethane. As a method of contraception, male condoms have the advantage of being inexpensive, easy to use, having few side-effects, and of offering protection against sexually transmitted diseases. With proper knowledge and application technique - and use at every act of intercourse - users of male condoms experience a 2% per-year pregnancy rate.