Nina (wearing Matte) is 5'11", usually wears a US size 8 and wears a size M here.
Amee (wearing Matte) is 5'2", usually wears a US size 0 and wears a size XS here.
Note: These trackpants rest higher on the waist. Size down for a more fitted, tailored look. Size up for a more relaxed, slouchy look.