[Moo] how to change the width off a or class

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hello, i would like to change the width of my dif class

.content_toggle {
                width:920px;
        background-color:red;
                }

to

.content {
                width:580px;
                }

i tried this:

 $('inhalt').toggleClass('content_toggle');
it change the color but not the width.

$('inhalt').setStyle('width', '580px');
works fine but i how to toffle this?

somebody can help?