A threesome is a form of group sex, but involving only three people. Practitioners have described going to public places such as a mall or a park. Contact mutual masturbation One person touching another person to masturbate. Interracial pornographic films have experienced an explosion in popularity, becoming one of the fastest-growing and biggest-selling genres. Fisting may be performed with or without a partner. Though the term anal sex most commonly means penile-anal penetration, sources sometimes use the term anal intercourse to refer exclusively to penile-anal penetration, and anal sex to refer to any form of anal sexual activity, especially between pairings as opposed to anal masturbation. Kinbaku is a Japanese style of bondage or BDSM which involves tying up the bottom using simple yet visually intricate patterns, usually with several pieces of thin rope . However, that term is usually applied to a male who observes somebody secretly and, generally, not in a public place. Cum shots have become the object of fetish genres like bukkake. Simultaneous penetration of the vagina by two penises or other objects. Seconds after being deposited onto the face, momsex the semen thickens, before liquefying 15–30 minutes later. Boot pornography includes women and sometimes men wearing gay twinks boots for their lesbian hentai sexual appeal. Solo pornography features performers masturbating. Transwomen are most often featured with male partners, but are also featured with other transsexuals or cissexual women. Another aspect is the structured training of the Bottom. As most porn is marketed to men, most bisexual porn is marketed to heterosexual or bisexual men. MILF pornography is a genre of pornography in which the actresses are usually women ages 40 to 50, though many actresses have started making pornographic movies at age 30 and older, while actresses have played MILFs as young as 24. The anal and rectal tissues are delicate and do not provide natural lubrication, so they can easily tear and permit disease transmission, especially if lubricant is not used.