Insertion in pornography features women inserting various odd objects into their anus or vaginas. It is also often mixed with hentai movies other fetishes in practice, such as voyeurism, denial, etc. Such films continued to be produced but could only be distributed by underground channels. Participants usually derive pleasure from this, even though many of the practices—such as inflicting pain or humiliation or being restrained—would be unpleasant under other circumstances. 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. Another variant of reality pornography consists of normal couples that are filmed by professionals, in which case the only obvious distinction from amateur pornography is the higher quality of production, filming and editing. The stimulation may involve hands, fingers, everyday objects, sex toys or combinations of these. Clothed female, naked male is a genre of erotica featuring one or more nude men and one or more clothed women. Interracial 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. Group sex can occur between people of all sexual orientations and genders. Reflective of its views on sexuality and culture, Japanese pornography delves into a wide spectrum of heterosexual, homosexual, and transgender sexual acts in addition to unique fetishes and philias. A common hot gay sex way that these are depicted in a single scene is with one woman and two men performing together. Since at least 1973, it has also nude milfs been used to refer to a sexually attractive young woman. This style of filming is in contrast to having a separate, third-person camera crew filming all the action. For other scenes, particularly in established relationships, a safeword may be agreed to signify a warning rather than explicit withdrawal of consent; and a few choose not to use a safeword at all.