I'm a kindergarten teacher, so I'm very active and don't have time to touch-up my make-up during the work day. The heat is frequently on very high and classroom teachers don't have control over the room's temperature. The excessive heat causes my drug-store brand eyeliner to smudge and eventually rub-off by the time my students are dismissed at the end of the school day. The MAC Fluidline Eye Liner is the ONLY product that stays in tact through excessive heat and exercise. LOVE this eyeliner! Thank you, MAC!