According wikipedia,a sex doll (also love doll or blowup doll) is a type of sex toy in the size and shape of a sexual partner for aid in masturbation. The sex doll may consist of an entire body with face, or just a head, pelvis or other partial body, with the accessories (vagina, anus, mouth, penis) for sexual stimulation. The parts are sometimes vibrating and may be removable or interchangeable.

140 CM 4.59ft Silicone Love Doll with Metal Skeleton 3 Entries Natural Skin Sex Toy for Male
Here I wanna talk about silicone sex doll,a life-size sex doll,which has realistic skin,skeleton,organs.You can dress her,make up her face,posture her,more important,you can sex with her like real woman.

153cm Silicone Sex Angel Doll with Metal Skeleton 3 Entries Lifelike Sex Toy
Although manufactory was making the love sex doll like human as much as possible ,it is far from flexible like a real human.Below brief drawing of silicone sex doll for your reference.You can see the love sex doll is supported by several metal joints life like skeleton in some key parts,which move range is limited.Thus,be gental when you play with love doll.

USEXDOLL realistic skeleton drawing