If you're used to Asian Ball-Jointed dolls, the term usually used for this size is 40cm Slim MSD. If you're used to Western Fashion Dolls, the term usually used for this size is 16" Fashion Doll. Surprisingly, though they evolved differently they can share clothes patterns!
This pattern size has the most variations so you can tuck in the waist for wasp-waisted dolls like 16" Fashion Royalty dolls, widen the chest for broad-shouldered dolls like Kid Delf and Soul Kids. The default settings on sizing is designed to best fit Fairyland Minifees and Tonner Ellowyne Wilde.