Change size of Android-Seekbar?

I have a question concerning seekbars. I tried several things but nothing helped. I want to change the height of the seekbar, but not the complete seekbar, only the bar where you scroll over with your thumb. I tried several things e.g. setBackGroundDrawable and setProgressDrawable and made my own drawables, but the drawable-size is fixed to the size of the Standard-Android-Seekbar. What can I do now?