High heel pornography involves women or men dressed in high heeled shoes. Reality Reality pornography refers to real or faked amateur encounters. Gloryhole pornography features women performing fellatio on unidentified men through a small hole made in a bathroom divider. 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. Masturbation has been depicted in art since prehistoric times and is mentioned and discussed in very early writings. Interracial pornography typically employs ethnic and racial stereotypes in its depiction of performers and many of interracial pornographic gay boy porn films still include racial stereotypes, although the segregation of actors by race has diminished considerably. Bobbi S. Bisexual DVDs sell much better online than in adult video stores, possibly due to customers in stores feeling embarrassed to buy them. Some BDSM practitioners prefer a code of behavior that differs from SSC and is described as risk aware consensual kink , indicating a preference for a style in which the individual responsibility of the involved parties is emphasized more strongly, with each participant being responsible for his or her own well-being. This technique may include the use of a simulacrum, or artificial vagina. It may involve sexual attraction to women who are pregnant or appear pregnant, attraction to lactation, or attraction to particular stages of pregnancy such as impregnation or childbirth. By Japanese law, the genitals of actors and actresses must be censored and up the mid-1990 so was the depiction of pubic hair. This may relate to fetishes such as voyeurism hentai sex or cuckolding. When he is in position the cover is closed. See Gay-for-pay. Group sex can occur between people of all sexual orientations and genders. It may be used as foreplay, or as an alternative to sexual penetration. Softcore pornography generally contains nudity or partial nudity in sexually suggestive situations, but without explicit sexual activity, sexual penetration or extreme fetishism, while hardcore pornography may contain graphic sexual activity and visible penetration, including unsimulated sex scenes.