Playbar SmallButton and BigButton

Hello everybody
I have made a custom Playbar. For this I have adapted an existing Playbar (CoolBlue) to my needs. I've made all the changes to the FLA file and the PlaybarIcons and everything works fine.

But I have a problem with the two different sizes of buttons .playbarBigButton and .playbarSmallButton inthe HTML output.
The Play and pause buttons are big and all other buttons are small.
But I would like to have the forward and back button large and all others small Play, pause, sound etc.

Where can I change the class playbarBigButton and playbarSmallButton for each button?
Do I make these changes in the playbarStyle.css file? If yes how?

Thanks in advance and many greetings
Mike