It has also been recommended as a form of foreplay or safer sex. Other fetish Bareback pornography features performers who are not wearing condoms. Several hundred exclusively pegging films were produced, as well as twice as many bisexual and straight films with strap-on scenes. The glans itself may widen and lengthen as the stimulation continues, becoming slightly darker in colour, while the gliding action of the foreskin reduces friction. There is, however, no third party camera work involved. The term combines elements of the Freudian psychoanalytic fetish and the Marxist commodity fetish, and is used in the context of British, Spanish and French colonialism and imperialism and their aftereffects. Common phrases used to refer to these individuals are chicks with dicks or the derogatory term shemale, although these are generally considered naked milf pejorative among transwomen. The term bondage describes the practice of Physical restraining. Pornographic films are typically categorized as either softcore or hardcore pornography. Mutual masturbation, mutual manual stimulation of the genitals between partners, can be a substitute for sexual penetration. Diaper fetishism is totally independent from pedophilia as the wearer derives pleasure only from the diaper and/or use of it. Sub-genres can also be classified into the characteristics of the performers or the 3d hentai type of sexual activity on which it concentrates, gay twinks and not necessarily on the market to which each sub-genre appeals. The industry generally refers to such films as adult films, which is part of adult entertainment. There has been an increase in discussion and portrayal of masturbation in art, popular music, television, films, and literature. Double penetration of the vagina, anus and mouth, can involve: Simultaneous penetration of the anus by two penises or other objects. Cuckolding can also be mixed with other non-monogamous relationship arrangements with which it has substantial overlap such as Swinging, wife-swapping, open relationships, and polyamory, etc.