Filler adds volume, shape, and definition. A lip flip uses a few units to relax the upper lip so it rolls outward — a smaller change for those who want more show without more volume.
Filler and the lip flip solve different things: filler adds volume, shape, and definition you can dial up or down, while a lip flip uses a small dose of Botox to relax the upper lip so it rolls slightly outward, showing more of the lip you already have without adding size. Some patients use one, some combine both, depending on whether the goal is more volume or more show.
This is general education, not a treatment plan. What you actually need depends on your anatomy, muscle strength, and goals — Rocio determines that with you in person.