I'm 5'5 and 120 pounds and you can see my underwear (both the outline and the pattern) through the leggings. They feel smooth but alas I can't wear these out in public like real leggings unless I wear a skirt or shorts underneath it.

Two stars since for anyone near my size, these are tights,not leggings, due to the very small fit and transparency. I'm disappointed in the sizing because the pattern itself is gorgeous, but this wouldn't fit most customers sadly. Even while I fit within the free sizing chart mentioned above, it's still too see through to wear in public.