The refill system matters only after the formula has earned a regular place in your routine. Sisley says the refill clips into the existing cap base after the upper lipstick section is removed. That can reduce the need to replace the decorative outer case, but only when you plan to continue using the same system.
Begin with the complete product if you do not already own a compatible case. Before buying another full case later, compare the available refill with the shade and finish you actually want. A refill is not automatically the better purchase if you are still testing whether sheer beige color, increasing shine, or this exact formula suits your routine.
Use a simple replacement rule: refill when the formula is already a repeat choice and the existing case remains functional. Choose a different product when you have learned that you need more opacity, less shine, or another shade direction. The refill format should support an established habit, not create pressure to stay with a product that misses the original need.
For more detail on keeping a soft lip shape clear, the Romantic lipstick placement guide covers shade placement and feathering. Use that technique after deciding that a sheer lipstick format belongs in the routine.
Use the final Romantic buying check