The idea behind it is that you twist the dial to the relevant number - 1 for day, 2 for night and 3 for ultra-glam. When I first saw the pack in Superdrug I was a little disappointed... it looks quite cheap and you don't get an awful lot for your money (as half the tube is taken up with the mechanism.) However, I went ahead and took one home to try.
I was pleasantly suprised! It's a nice touch to be able to use the same mascara for different times of day - there was a real visible difference between the dials. Although the third dial was a bit too clumpy for me, it definately gives an ultra-voluptuous look. I always have about four different mascaras in my make-up bag and quite often use one over another to get added volume, so this new addition to the Rimmel range will most certainly save me time, space and money.
I do think this is a bit of a gimmick though that people will get bored of - it's fun for the time being, but will we all revert back to our usual products in a few weeks? Only time will tell!