Interracial gay group sex pornography typically employs ethnic and racial stereotypes in its depiction of performers and many of interracial pornographic films still include racial stereotypes, although the segregation of actors by race has diminished considerably. It spawned numerous sequels, several of which won porn milf nude celebrities adult film awards. Emetophilia pornography involving vomiting and gagging. Lesbian pornography made for women is usually made by women, and usually features women who identify as lesbian or bisexual. The genres of pornography are based on the type of activity featured and the category hentai movies of participants, for example mateur pornography is a category of pornography that features models, actors or non-professionals performing without animated porn pay, or actors for whom this material is their only paid modeling work. Gay-for-pay describes male or female actors, pornographic stars, young gay porn or sex workers who self-identify as heterosexual but who are paid to act or perform as homosexual professionally. The term is a slang word that originated in the gay community and comes from the equestrian term bareback, which refers to the practice of riding a horse without a saddle. While bondage is a very popular variation within the larger field of BDSM, it is nevertheless sometimes differentiated from the rest of this field. Mutual masturbation can be practiced by males or females in pairs or groups with or without actually touching another person as indicated by the following examples of contact versus non-contact scenarios: Non-contact mutual masturbation Two people masturbating in the presence of each other but not touching. The anus has a relatively high concentration of nerve endings and can be an erogenous zone, and the receiver may receive pleasure from external anal stimulation. Examples of heterosexual pornographic film series featuring creampies include Cream Filled Teens and Internal Cumbustion. Performers are usually clean-shaven, thinner and more effeminate than ones in mainstream gay pornography.