bucutie2-
they say that because you can return them for a refund after using the tops if they don't work but ONLY if you still have all the bottom strips. once i saw they worked, i started wearing the tops and bottoms together and it works just fine.
here's a tip --the bottom strip still has half the "stuff" still on it. cut it into 2 rectangular pieces to put on the sides of your bottom teeth. that way the sides get white too! it doesn't stay in place that well unless you keep your mouth closed, but that's not that hard for 30 minutes (well, unless you like to talk a lot!). also, for the top strips--since the sides don't get whitened, start out one day putting the strips all the way to the left side of your mouth. then the next day put it on the right side. that way it evens out and your middle teeth are covered every day.
as you can see i am a whitestrip addict!
i have my own little systems and everything!
happy whitening!