I have three.
Can anyone tell me what the black one is used for? I got it as a gift, but it's not as good as the pink/purple imo.

The purple I bought two summers ago, still haven't used it up as you can see.
I only use it when my hair gets longer.
The pink is my second one. If I'm not lazy, I use it almost all the time.
Two years, I hardly use the black one.