Ass to mouth pornography shows the transfer of a performer penis from a second performer anus to that same second performer mouth in a single shot. For uncircumcised males, stimulation of the penis in this way comes from the pumping of the foreskin, in which the foreskin is held and slid up and down over the glans, which depending on foreskin length, is completely or partially covered and then uncovered in a rapid motion. The term lesbian is also used with regard to sexual identity or sexual behavior, regardless of sexual orientation, or as an adjective to characterize or associate nouns with female homosexuality or same-sex attraction. Bareback sex is physical sexual activity, especially sexual penetration, without the use of a condom. Others may also use vibrators and other sexual devices more commonly associated with female masturbation. One or more of the participants may engage in autoerotic sexual activity, such as masturbation, possibly without physical contact with the other participants. In addition to mainstream pornography, the popularity of facials has led to creation of its own niche market, like video series that specialize in showing the act. Creampie scenes depart from heterosexual pornographic convention in favor of a depiction that more closely mimics sexual intercourse as performed in ordinary life; they have been called the counterimage of facials. Facial cum shots are currently regularly portrayed in pornographic gay video films and videos, often as a way to close a scene. The term soft crush refers to the more common fetish surrounding videos involving inanimate objects or small invertebrates being crushed, while the term hard crush refers to such videos involving larger animals with vertabrae, and arguably more pain-susceptible animals . Although pornography has usually focused on heterosexuality, due to the prevalence of the heterosexual orientation, explicit gay material has a long history as well, which reaches back to Greek antiquity, if not to prehistory.