When I create my Android app i create 6 drawable folders:

1. drawable-hdpi. // resolution 1.5 x
2. drawable-mdpi. // resolution 1 x
3. drawable-xhdpi. // resolution 2 x.
4. drawable-large. // resolution 2 x.
5. drawable-xlarge. // resolution 2.5 x.
6. drawable-xxhdpi. // resolution 3 x.

In every folder i put the same image with different size according to android device resolution and screen size.

Is this correct? or this is insufficient for my android app ?