The inner jaw of the xenomorph is the greatest sexual invention to come from modern art. It is prehensile and of uniform thickness, aside from the head, meaning it is perfect for penetration. The tongue inside is an added benefit, and due to the excessive amounts of saliva, it can lubricate any orifice it enters.
It also is wonderful for fellatio. It’s tight, great for pleasuring a penis, and is a fully functioning mouth. It could also excel at cunnilingus and annilingus, making it versatile. Aesthetically it’s sexy as fuck, and it’s attached to a larger sexy alien you could fuck after foreplay with the inner jaw, or you could finish in the inner jaw after fucking the xenomorph. Truly a utilitarian fucking machine.