The primary subjects of pornographic depictions are pornographic models, who pose for still photographs, and pornographic actors or porn stars, who perform in pornographic films. Group sex pornography features at least two men and two women , usually more, who all perform sex acts on each other. Reality pornography is a genre of pornography where staged scenes, usually shot in cinéma vérité fashion, set up and precede sexual encounters. Shotacon : Similar to Lolicon, this genre involves prepubescent or under-aged boys between the ages 6–12. Cartoon pornography depicts illustrated or animated fictional characters in erotic and sexual situations. Mammary intercourse has sometimes been considered a perversion. 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. Production young gay porn of such films was profitable, and a number of producers specialised in their production. These actors often play the top roles but this is not always the case, such as with Kristen Bjorn and some Bel Ami models. This makes varying degrees of stimulation an integral part of oral sex for many men. Pantyhose/Tights/Stockings pornography involves women or men dressed mature milfs in pantyhose, tights, or stockings. A scene where many women have sex with one man is referred to as a reverse gang-bang. Preggo pornography features pregnant performers and may include erotic lactation as a fetish. Testosterone discourages fat storage in these areas. They signal the presence of estrogen and the presence of sufficient fat stores for pregnancy and lactation. Creampie pornography features ejaculation inside the vagina , mouth or rectum instead of the common hentai videos cum shot, followed by the visible seeping or dripping of semen from the vagina, mouth or anus. Female masturbation involves the stroking or rubbing of a woman vulva, especially her clitoris, with an index or middle fingers, or both. Contrary to the other two types, B/D does not define the Tops and Bottoms itself, and is used to describe the general activities with either partner being the receiver and the giver.