ExtJs - form component styling

I am trying to remove the border of form fields in Extjs. Currently I have it working on textfields using :

fieldStyle: 'border:none 0px black;background-image:none',

However applying the same config to combo's and datefields dosen't seem to work the fields still have the border around them. Anyone have any ideas why or any styles I seem to be missing here?

Thanks in advance!