MAC Romantic Overture is a warm sheer with a sparkle finish that is limited edition and retails for $20.00. In comparison, Guerlain L'Oiseau de Feu (901) is a neutral sheer with a pearl finish that is limited edition and retails for $30.00.
Guerlain L'Oiseau de Feu (901) is 90% similar — it is less shimmery.
