Since I'm a Volks person--as I said before--I'll focus on the Volks brand throughout the tutorial. However, Obitsu's properties are very similar to Volks'. So if you see a certain size in Volks that you like, you'll probably be able to find it on an Obitsu website, too.
CHILD SIZE - 8" doll: Perfect for making little girls and boys. Elenore (The 3rd doll in the picture) and Little Rakikai are both child size dolls.
FEMALE - 11" doll: You can choose what size chest you'd like to personalize your character. Alexandra--also known as Hexia, is shown above with her insane Mohawk hairstyle.
TEENAGED BOY - 11" doll: The exact same size as the female doll. Very slim, this doll is good for making a teenaged boy, or a more frail character. The body was perfect for Aru, the last doll in the line above.
SLIM MALE - 11.5" doll: A body for an older teenager or a lean, full-grown adult man. It has a thicker chest, making it seem healthier than the teenaged boy doll. Ryou, the second doll in line, has this body style.
NEO & NEO-GO - 11.5" doll: These dolls are thick-chested and really represent a male figure. Pegasus, the first doll in line (remember Pegasus? My childhood idol?) is made with a NEO-GO body. More about them later on.
DOLLFIE DREAM, SUPER DOLLFIE & SUPER DOLLFIE 13 - 2' doll: These are supersized, fully articulated dolls with amazing detail. They're the same size as Thiefy, the fourth doll in the line above.
MINI SUPER DOLLFIE - 1' doll: The child-size version of the Super Dollfie.